ALEXA Family Frequently Asked Questions

Welcome to the frequently asked questions about the ALEXA family of cameras as of June 1, 2015.
This FAQ pertains to general topics concerning all ALEXA cameras and the ALEXA, ALEXA Plus, ALEXA Plus 4:3, ALEXA M and ALEXA Studio with Software Update Packet 11 in particular. Some ALEXA XT/XR/SXT/SXR issues are also covered, but detailed information about ALEXA XT cameras and the XR Module upgrade can be found in the ALEXA XT/XR FAQ, and detailed information about ALEXA SXT and SXR cameras can be found in the SXT/SXR FAQ. Directions given are always from the operator’s point of view. This FAQ supersedes any earlier versions. To avoid redundancy, information contained in the ALEXA web pages or manual will not be duplicated here.
More FAQs can be found here:

ALEXA SXT/SXR FAQ
ALEXA XT/XR FAQ
Visual Effects FAQ
ARRIRAW FAQ



1. GENERAL
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What can I do to familiarize myself with ALEXA?

There are a number of simple steps you can take in the cozy comfort of your home. 

 

  • 1. Read the ALEXA web pages. We have added a lot of useful information over the years about everything ALEXA. 

  • 2. Read this FAQ. It contains many important questions that have been asked by other filmmakers. 

  • 3. A lot of the practical information you may need on the set has been summarized in the ALEXA Pocket Guide

  • 4. To familiarize yourself with ALEXA’s control panel you can use the ALEXA Camera Simulator



  • 5. Look at the ARRI Tech Talk videos which give a short introduction to many ALEXA related topics. 

  • 6. Read the ALEXA Manual

 

Of course, the best way is to talk to your local rental house and play with an ALEXA when it is available, or, even better, shoot a test. 

What online tools do you have available for ALEXA?

There are a number of online tools we have created to make working with ALEXA easier and more powerful.


ALEXA Frameline Composer (AFLC)
With the ALEXA Frameline Composer you can create custom frameline files online, which can be downloaded to your computer and then copied to the ALEXA SD card. Place the SD card into an ALEXA to view the custom framelines in the viewfinder or on the MON OUT HD-SDI outputs. The AFLC can create framelines for 16:9, 4:3 Full, 4:3 Cropped and Open Gate sensor modes. Up to three framelines can be placed in the same file to be displayed simultaneously from the camera. In addition, the AFLC offers a number of predefined framelines for your convenience for all recording formats. 





ARRI Lens Illumination Guide (LIG)
The ARRI Lens Illumination Guide (LIG) is an interactive visual guide that shows how different lenses illuminate different sensor modes and target aspect ratios of ARRI ALEXA and AMIRA cameras. Each lens type is designed to cover a certain image circle, within which the manufacturer upholds image quality criteria, including illumination. Lenses still show an image outside of this image circle, but of an undefined image quality. Farther out there is a point at which there is no more light, defining the 'illumination circle'. The size of the illumination circle changes based on lens design, focal length, focus setting and iris setting, which are all parameters that can be set in the LIG. 




The ALEXA Camera Simulator

The ALEXA Camera Simulator allows you to familiarize yourself with ALEXA’s control panel.

 

LUT Generator
For viewing Log C images directly on the set and for color correcting in post, look up tables (LUTs) are used. These can be generated by our online LUT Generator.

While Log C images provide the greatest flexibility in post, viewing them directly on a regular monitor provides a washed out and desaturated image and will freak out the director. A LUT transforms the digital signal to show a color correct video signal for monitoring. Typical applications of LUTs in combination with Log C images include creating previews of Log C images on the set, converting Log C images for dailies, converting Log C images in the display path for color correction and, last but not least, a round trip conversion of Log C to linear data for VFX workflows.

 

The ARRI online LUT Generator can create more than 20 different target file formats for a wide range of software and hardware systems. These LUTs are divided into four groups: On-set LUTs, Dailies LUTs, Postproduction LUTs and Advanced postproduction LUTs. As specific needs may vary by project and 3rd party LUT formats are subject to change, we recommend that you test these LUTs before using them in production.

 

Please note that the ARRI online LUT Generator is not designed for creating ARRI Look Files, but rather Look Up Tables for third party equipmnet.

 

Can I update an ALEXA or ALEXA Plus to an ALEXA Studio?

No. The ALEXA Studio has a different housing, contains different electronics and requires different testing and calibration for its 4:3 sensor. Updating an ALEXA or ALEXA Plus would be prohibitively expensive, and so we do not offer it as an option.

Can I update an ALEXA with a 16:9 sensor to an ALEXA with a 4:3 or Open Gate sensor?

No. All three sensor types, 16:9, 4:3 and Open Gate, require different electronics, different testing and different calibration. Updating a camera with a different sensor would be prohibitively expensive, and so we do not offer it as an option. 

Which ALEXA has which license included?



Licenses that are not included can be purchased at the online license store.


Note:
ALEXA SXT7SXR cameras do not support DNxHD and so the DNxHD license cannot be used.

How can I create a 4K deliverable with an ALEXA?

Depending on the ALEXA Model, there are different paths to a 4K deliverable. Please note that we distinguish between the 4K DCI (4096 x 2160) distribution format, which is used for a cinema release, and the 4K UHD (3840 x 2160) distribution format, which is used for UHD TV deliverables.

ALEXA Classic Cameras (EV, Plus, Plus 4:3, M, Studio)
With an ALEXA Classic you can shoot 16:9 ARRIRAW (2.8K) and do the up-sample to either 4K Cine or 4K UHD in post. This method has been used successfully on many feature films, including Skyfall, which even had an IMAX release, as well as The Avengers, X-Men and many others. ALEXA's stellar and unbeaten exposure latitude, extended clean highlights and low noise floor, high sensitivity, great color separation and natural skin tones not only deliver sharp and stunning images in a class of its own, they also up-sample beautifully.

ALEXA XT Cameras (XT, XT Plus, XT M, XT Studio)
With ALEXA XT cameras you can, of course, also shoot 16:9 ARRIRAW (2.8K) and up-sample in post, but the XT camera provide two additional options:

1. Shoot Open Gate ARRIRAW (3.4K) and do the up-sample in post. This is the path a number of high end feature films are taking for a 4K DCI deliverable now. Please note that ALEXA Classic cameras with the XR Module Upgrade do not support Open Gate.

2. Shoot 16:9 ProRes 3.2K and do the up-sample in post. This is what we would recommend for TV series looking for a 4K UHD deliverable, since the data rate (assuming ProRes 4444, which most seem to be using with ProRes 3.2K) is lower than ARRIRAW and since the less expensive media (SxS PRO, SxS PRO+ or CFast 2.0) can be used. Shooting ProRes 3.2K and doing an up-sample at the end of post has one great advantage: you do not carry the full data load of a 4K image from the set through post, which means a more efficient post workflow. ALEXA Classic cameras with the XR Module Upgrade do support ProRes 3.2K. ProRes 3.2K requires ALEXA Classic/XT Software Update Packet (SUP) 11.0 or later.

ALEXA SXT/SXR Cameras (SXT/SXR, SXT/SXR Plus, SXT/SXR Studio)
ALEXA SXT/SXR cameras provide the same options as ALEXA XT cameras, but since they contain the ALEXA 65 electronics with a lot of extra horse power, they offer these two additional options:

1. Record 16:9 ProRes 4K UHD directly in-camera. 3.2K (3200 x 1800) from the sensor is up-sampled in-camera by a factor of 1.2 to create and record ProRes 4K UHD (3840 x 2160).

2. Record Open Gate ProRes 4K Cine directly in-camera. Open Gate 3.4K (3414 x 2198) from the sensor is up-sampled in-camera by a factor of 1.2 to create and record ProRes 4K Cine (4096 x 2636). This is actually a taller image than the required 4K DCI distribution format (4096 x 2160), so there is ample room for up/down re-positioning in case a microphone makes an appearance at the image top or the dolly track shows at the image bottom edge.

Please note that AMIRA and ALEXA Mini also support 4K UHD in-camera recording, but only ALEXA SXT/SXR cameras offer 4K Cine in-camera recording.

Is ALEXA the right camera for special effects?

Yes. ALEXA's extremely wide exposure latitude, low noise floor and clean color separation turn out to be critically important for good compositing results, as can be attested by numerous VFX supervisors, including Rob Legato, who won an Academy Award for best VFX on Hugo, which was shot with ALEXA. For a further testimonial by a VFX supervisor of a blockbuster Hollywood movie take a look at the sidebar in the ARRINEWS "Avengers Assemble" article, or read the full article here. 

2. ALEXA AND LENSES
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Which lenses can I use with ALEXA?

All modern 35 format PL mount lenses can be used with all ALEXA cameras except the Optimo DP zooms, which are not compatible with ALEXA Studio and ALEXA XT Studio.

Can I use anamorphic lenses with ALEXA?

Yes. You can use both traditional anamorphic lenses with a 2x squeeze factor (like the ARRI Master Anamorphic lenses) as well as anamorphic lenses with a 1.3x squeeze factor with ALEXA cameras.

For the most effective use of 2x squeeze anamorphic lenses, the ALEXA 4:3 sensor is the same size and shape as a Super 35 mm film frame. A 4:3 sensor is crucial for delivering the unique and cinematic widescreen look that can trace its origins back to the CinemaScope films of the 1950s. It is a look that has long been appreciated by cinematographers, directors and the viewing public.

In the graphic below you can see on the left side the film/sensor area used by film cameras (orange) and ALEXAs (blue), which are almost identical. The 1.95:1 area is the area used by an anamorphic lenses. 2.39:1 is the anamorphic projection aspect ratio, and the lens squeezes the image by a factor of two, so 2.39 divided by 2 = 1.195. On the right side you can see the significantly smaller area used for anamorphic lenses by a camera with a 16:9 sensor. 


Will there be a shading artifact with ALEXA?

No. Shading (or "portholing") is an effect that occurs when a lens is used with light rays that are at a large angle to the optical axis and some of those rays get obstructed either by a micro lens and/or don't reach into the little well each pixel is situated in.

ALEXA has relatively large photosites and shading is much less prominent with larger photo cells than it is with small cells. Additionally, we have tested the Master Anamorphics, Master Primes, Ultra Primes and the Alura Zooms, and found that their light rays have no steep angles (= they have a 'near-telecentric' design) that would cause shading with ALEXA's sensor.

3. EXPOSURE AND FILTERS
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Does ALEXA’s exposure latitude change with different Exposure Index (EI) settings?

No, it does not. Most digital cameras have the greatest exposure latitude at a specific EI setting (often called the 'sweet spot'). Choosing an EI setting that is higher or lower than the optimal setting will result in a sometimes surprisingly large loss of exposure latitude. ALEXA is unique in that its exposure latitude of over 14 stops (as measured with the ARRI Dynamic Range Test Chart (DRTC)) stays constant from EI 160 to EI 3200. 

What happens when I change ALEXA’s Exposure Index (EI) setting?

While ALEXA's 14+ stops of exposure latitude (as measured with the ARRI Dynamic Range Test Chart (DRTC)) and unique highlight handling approaches that of film, there is one major difference between the way film and digital cameras behave: with digital cameras, a change in EI will shift how many stops are available above and below 18% grey - each EI step shifts the location of 18% grey. 



As a shortcut, we have come up with the following method of writing ALEXA’s exposure index:

 



Values behind the exposure index are the number of stops above and below 18% grey. These values are for Log C. Rec 709 and DCI P3 have 0.5 stops fewer in the low end at EI 160, 0.4 stops fewer in the low end at EI 200 and 0.2 stops fewer in the low end at EI 400. Otherwise they are the same.

How does the ALEXA Studio mirror shutter determine exposure?

A detailed description of electronic and mirror shutter functioning, the resulting consequences for the cinematographer and some practical tips on using both shutter modes with the ALEXA Studio can be found in the "ALEXA Studio Electronic and Mirror Shutter" white paper available on the ARRI download web page. Click here to access the white paper

Can I use traditional ND filters with ALEXA?

While traditional ND filters work great for film, digital camera sensors behave differently and require different filters. For all ALEXA models, except for the Studio models (ALEXA Studio models have their own motorized sliding ND filter mechanism), we offer the ARRI Full Spectrum Neutral Density (FSND) filters as an upgrade. The FSNDs maintain a neutral color balance at all densities. 


Click here to see the FSND spectral response graphs 


Click here to see the FSND sample test images 

Why is the Internal ND Filter in the ALEXA Studio ND 1.3?

The ALEXA Studio has a sealed sliding mechanism that can place either an optical flat or an ND filter in front of the sensor. However, there is precious little space between the rotating mirror shutter and the sensor where these filters are located. The only high quality optical ND that is thin enough is an ND 1.3. This is the equivalent of 4.3 stops of light attenuation. 

How much Infrared does the ALEXA Studio internal ND filter cut?

The ALEXA Studio has a sealed sliding mechanism that can place either an optical flat or an ND filter in front of the sensor. The optical flat provides essentially the same infrared filtering capability as the cover glass in the other ALEXAs. The ND filter cuts more infrared, with an effectiveness somewhere in the middle between the optical flat and commercial IR cut filters. As always, we suggest tests to see if you need to use additional IR cut filters when using the Studio's internal ND filter. 

Can the full exposure latitude of ALEXA be recorded as ProRes or DNxHD?

The short answer is: yes, the full exposure latitude of ALEXA can be recorded as ProRes or DNxHD. The long answer is this: The ALEXA sensor can capture over 14 stops (as measured with the ARRI Dynamic Range Test Chart (DRTC)) of exposure latitude. This image data is processed internally in a 16 bit format. Whenever this data is converted to an output, be it the 12 bit ARRIRAW, 10 bit HD-SDI, 12 bit ProRes 4444, any of the 10 bit ProRes formats, the 8 bit DNxHD 145 or the 10 bit DNxHD 220x or 4444, the whole exposure range of the captured image is mapped from the 16 bit range into the respective target range (see graphic).

So while the range from brightest to darkest image content remains the same, what changes are the number of different lightness levels in between. A 12 bit image has more steps between the brightest and the darkest parts than a 10 bit image. If there are not enough steps between the brightest and the darkest part of the image, you will see banding artifacts, where, rather than seeing a gradual change in lightness, you will see distinct bands of lightness.



I see double reflections in my Image. What is that?

This is not an ALEXA issue, but a filtration issue. When using more than one filter in the matte box, it is very easy to get reflections from the many glass surfaces in play. There are now a couple of methods to avoid these reflections in addition to the traditional methods (careful lighting and the copious use of flags on stands and eyebrows on the matte box):  

  • Use ARRI Full Spectrum Neutral Density (FSND) filters inside the camera instead of external ND filters. An upgrade kit is available that can install the filter holder in any ALEXA Classic camera (except ALEXA Studio). ARRI FSND filters sit between the lens and the sensor, have a perfect color balance even at higher densities and reduce reflections and other unwanted optical effects.
    For more information, click here
  • Use the ARRI Studio Matte Box SMB-1, which can tilt its filter stage to remove unwanted reflections.
    For more information, click here
I see some noise at low fps and wide open shutter. Is that normal?

ALEXA allows setting the exposure time longer than 1 second per frame (i.e. 358° shutter at 0.75fps = 1.33 seconds per frame). Doing so will increase noise and cause individual pixels to light up. To achieve optimum image quality at slow frame rates the exposure time should not exceed 1/25th of a second.

Should I use the camera's white balance settings or color correction filters instead?

Using the camera's built-in white balance settings is preferable to color correction filters in front of the lens. A color correction filter will always take away light from all three colors, so all three will have to be amplified, which leads to more overall noise. Using the camera's white balance setting instead will only amplify those color channels needed to achieve a neutral color balance. 

What is the native color temperature of ALEXA’s sensor?

The short answer is that while ALEXA does not really have a 'native' color temperature, the point at which the lowest overall gain is applied to the red, green and blue channels is at 5600 degrees Kelvin, yielding the lowest possible noise in the image. However, since ALEXA has an amazingly low noise level anyway, the difference in noise between 3200K and 5600 K is so minimal as to not be relevant in most shooting situations. So choosing the color temperature can be dictated by other factors, such as the cinematographer’s preference or the availability and/or cost of tungsten or daylight lighting instruments.

For the long answer, we have to start with the birds and the bees, or in our case, with celluloid and silver halide crystals. Film stocks are balanced for either a tungsten (3200 degrees Kelvin) or a daylight (5600 degrees Kelvin) light source. To achieve this, film manufacturers carefully tune the chemistry of the individual color layers. A grey card filmed under the respective lighting conditions should also result in a grey image after development. Thus each film stock has a given color temperature ‘baked-in’, which is sometimes also called the ‘native’ color temperature of that film stock. If you need a different color temperature, you change film stocks.

The way light is converted to an image is different for film and sensors. In order to display a grey card as grey, digital cameras have to carefully balance the gain applied to the red, green and blue (RGB) signals. The response of a digital camera to incoming light of different colors is determined by the response behavior of the filter pack (IR, low pass, UV), the Bayer mask inks, the photocell and the image processing. Even though the properties of the filter pack, Bayer mask inks and photocells are chosen with the best color balance in mind, there are other factors that also influence the color balance of the signal coming from the sensor, including an optimization for highest sensitivity, widest dynamic range and lowest noise. The proper balance between all those requirements is not only difficult to achieve, but also one of the factors that differentiates the various models of digital cameras.

Since one can neither create a sensor for each color temperature, nor change them if one could, digital cameras have to cover a variety of color temperatures with one sensor. For any given color temperature, a sensor will deliver an unequal amount of red (R), green (G) and blue (B) signal. In order to balance the three colors for different color temperatures, digital camera manufacturers use different amplification settings for red and blue, while keeping green unamplified. Let’s look at the actual settings ALEXA uses to illustrate this.

When using ALEXA to capture a grey card lit with a tungsten source (3200 K), the signals from the red and blue pixels have to be amplified by the following amounts to make a neutral grey:

R - 1.13x
G - 1.00x
B -  2.07x

Shooting the same chart, but now lit with a daylight source (5600 K), will put more blue and less red light on the sensor. So we can apply less amplification to the signal from the blue pixels but need a little more amplification for the signal from the red pixels:

R - 1.64x
G - 1.00x
B - 1.37x

So, for tungsten ALEXA uses a little more amplification in the blue channel, and for daylight a little more in the red. And for those who are still reading and want more: even though the red and blue amplifications are equal at 5000 K, the color temperature of 5600 K has the mathematically lowest overall noise gain, measured as the square root of the sum of the squared gains. 

Can the sensor be damaged by a laser?

Yes. Sensors are different from the human eye, and even in environments that are nominally safe for humans (like a laser show, for example), it is possible to damage the sensor with a laser beam. If and how the sensor is damaged depends on a number of factors, including the lens' focal length, lens iris setting, lens focus setting, the laser power, projected pattern and for how long the sensor is exposed to which part of the laser pattern. Thus the warning in the ALEXA Manual: 



I see something dark in very overexposed image areas. What is that?

An area that is overexposed more than eight stops above clipping can appear darker than its surroundings. 

4. POWER
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What are ALEXA’s power inputs?

ALEXA has three possible power inputs: the BAT connector, the battery adapter back and the battery adapter top. There are different battery adapters available for V-lock or Gold mount batteries. If more than one power source is available to ALEXA, the camera will automatically pick the power source with the highest voltage. Power sources can be attached and removed without powering the camera down first. 

What are the minimum and maximum power voltages for ALEXA?

ALEXA will accept any input from 10.5 to 34.0 V DC on any power input. Most 14.4, 24 and 26 Volt batteries and power supplies will work fine, as long as they can supply at least 100 W. While most 12 V batteries will work, they can quickly discharge below the 10.5 V limit and thus are not recommended. While most 30 V batteries will work, they will supply above the 34.0 V limit when fully charged and thus are also not recommended.

When do I get battery warnings and battery errors and what do they mean?

We distinguish between two types of batteries and two low power indications. Smart batteries can communicate with the camera, and normal batteries cannot. When the battery runs low, the camera issues a power warning, and when it runs even lower a power error. Once the camera reaches the power shut off level of 10.5 Volt, it will turn off no matter what batteries are used.

Power Indications for Normal Batteries

 

  • 1. The voltage level at which a power warning occurs is 12 V by default, but can be set in MENU > SYSTEM > POWER to another value. A power warning will be indicated in the camera display by a white “i” icon appearing on the left side and by a blinking BAT 1 or BAT 2. More information on the warning can be had by pushing the INFO button to the left of this “i” icon. If the camera status lines are turned on for the viewfinder and/or for the MON OUT output, they will also show a white “i” symbol. During a power warning the camera will continue to function normally.
  • 2. If the voltage falls to 10% below the set warning level (i.e. 10.8 V assuming a power warning level of 12 V), the camera gives a power error. A power error will be indicated in the camera display by a red “i” icon appearing on the left side and by a blinking BAT 1 or BAT 2. More information on the warning can be had by pushing the INFO button to the left of this “i” icon. If the camera status lines are turned on for the viewfinder and/or for the MON OUT output, they will also show a red “i” symbol. A power error changes the camera’s behavior. If the camera is recording to an internal card or drive, it will attempt to continue recording until it reaches the shut off level. If it is in standby, it will not allow you to start recording to an internal card or drive, but will stay powered on until it reaches the shut off level.


Power Indications for Smart Batteries

  • 1. The voltage level at which a power warning occurs is 10% of the battery’s full capacity and cannot be changed manually. A power warning will be indicated in the camera display by a white “i” icon appearing on the left side and by a blinking BAT 1 or BAT 2. More information on the warning can be had by pushing the INFO button to the left of this “i” icon. If the camera status lines are turned on for the viewfinder and/or for the MON OUT output, they will also show a white “i” symbol. During a power warning the camera will continue to function normally.
  • 2. If the voltage falls to 5% of the battery’s full capacity, the camera gives a power error. A power error will be indicated in the camera display by a red “i” icon appearing on the left side and by a blinking BAT 1 or BAT 2. More information on the warning can be had by pushing the INFO button to the left of this “i” icon. If the camera status lines are turned on for the viewfinder and/or for the MON OUT output, they will also show a red “i” symbol. A power error changes the camera’s behavior. If the camera is recording to an internal card or drive, it will attempt to continue recording until it reaches the shut off level. If it is in standby, it will not allow you to start recording to an internal card or drive, but will stay powered on until it reaches the shut off level.
What is ALEXA’s power draw?

The power draw of the ALEXA Classic camera and viewfinder is about 85 W and an ALEXA XT draws about 90 W. The power supply should deliver an output of more than 100 W to power the camera and viewfinder sufficiently. Additional accessories such as lens motors will add an additional power draw. Except for the ARRI HDM-7, which draws relatively little power, it is recommended to power on-board monitors from an external source. Please note that using a 24 V power source is more efficient than using a 14.4 V source, as ALEXA uses 24 V internally. 

What kind of on-board batteries are compatible with ALEXA?

Any battery that fits to a Gold mount or V-lock can in principle be used on the respective battery adapter of ALEXA. For all of those batteries, ALEXA can measure and display the battery’s voltage.
Please note that Anton/Bauer recommends against using the following battery types with ALEXA, since they would have short run-times and are not rated to handle such power requirements, which could reduce their life expectancy: ProPac 14, Digital ProPac 14, TrimPac 14, Digital TrimPac 14, HyTRON 50, DIONIC 90. Also note that the PAG-L190e is so wide that it obscures access to the connectors on ALEXA’s back/right side.
For Anton Bauer and IDX batteries ALEXA can communicate directly with the battery and display the battery capacity in percentage, which is a more accurate measure of how much longer the battery will last, especially with Lithium-ion batteries. We are working with other battery manufacturers to increase the number of batteries that can communicate with ALEXA.

Why are there no power tabs on the ALEXA battery adapters?

Most on-board batteries are capable of powering ALEXA and the accessories attached to ALEXA. Putting any further drain on them can result in significantly shortened battery life and problems. This is why we consciously did not put a power tab on the ALEXA battery adapter.

Why does the battery display sometimes switch from percent to voltage?

ALEXA can actively communicate with some on-board batteries (currently Anton Bauer and IDX) in order to display the battery capacity, which is a more accurate indication of remaining battery life than the default voltage indication. However, as long as a heavy accessory power load is applied to the camera, ALEXA can only display voltage, not capacity. As soon as the load is reduced, the indication will show capacity again. This issue only influences how the battery strength is displayed and has no influence on any other camera functions.

Please note that when the battery strength is displayed by voltage, the camera will display the battery low warning based on the battery low warning limit set in the SYSTEM > POWER menu, and not based on the battery capacity as communicated by the battery.

5. WORKING ON THE SET
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How can I mount third party recorders onto ALEXA?

The easiest way is with the CODEX/ALEXA Onboard S Bracket Set from ARRI (K0.60188.0). It is an articulated solution that attaches to the ALEXA Camera Center Handle and holds the CODEX Onboard S recorder or other third party recorders without cluttering up the camera.
Alternatively, there are many 3/8-16 UNC attachment points on ALEXA, and a number of M4 attachment points on the top surface of the camera for attaching third party recorders. Many recorder manufacturers already have brackets in their program that attach to the top of ALEXA and to their respective on-board recorders.

Please note that the Center Camera Handle CCH-1 (K2.72007.0) cannot be used together with a top mounted on-board recorder. Instead, use the Side Camera Handle SCH-1 (K2.72016.0) together with the Adjustable Center Grip Tall (ACG-2, K2.72022.0).

Why is there no display on ALEXA’s left side?

ALEXA has no display on the camera left side since there is no good place for it. ALEXA is smaller than a film camera and has no 'chin' that would house a mirror shutter, so there is no place that would not be covered by the operator. Thus any display would be inaccessible to the assistant while shooting.
However, it is still possible to change camera settings from the left side. The most important buttons are available to the assistant and the operator can monitor and change the most important settings in the Electronic Viewfinder EVF‑1. Additionally, the Wireless Control Unit WCU-4 and the Remote Control RCU-4 provide remote control capabilities anywhere near or far from the camera.








Can I connect the headphones while the camera is running?

No. Connecting the headphones while the camera is running can, in rare cases in environments with heavy static electricity, lead to a brief shut-down of the audio circuit. The audio circuit will reboot automatically, but some audio will not be recorded. Always attach and detach the headphones connector while the camera is not recording.

Why does the timecode on ALEXA’s display show a delay?

The timecode displayed in the camera‘s display shows some delay in reference to the actual timecode signal. The display is meant as a reference to check if the timecode values are correct, but is by no means frame accurate. Don‘t use the display to check Timecode frame accuracy. The recorded timecode is, of course, frame accurate.

Can I use reel numbers above 999?

No. ALEXA’s reel counting system only works up to 999 reels.

Will I get rolling shutter artifacts when shooting with ALEXA?

That depends on the speed of the event you are capturing. ALEXA uses a CMOS sensor with a rolling shutter. The pixels are read out from the sensor sequentially, starting at the top left of the image and then read line by line until the bottom right is reached. It is possible that a fast event, like a photographer's flash, is over when only part of the sensor has been read out, leading to a frame only partially exposed by the flash. It is also possible that straight vertical lines will be slightly bent during a fast pan (an effect sometimes called "skew"). However, ALEXA's read-out speed is very fast, so this effect is not very prominent.

The ALEXA Studio can be used in electronic shutter mode, in which case it functions like all other ALEXAs and like described above, but it can also be used in rotating mirror shutter mode, in which case a physical, half moon shaped mirror (see image) rotates in front of the sensor. This mirror shutter has the function of a global shutter. While the light strikes the sensor, the pixels are exposed and accumulate a charge. When the mirror fully covers the sensor, the charge is read out. This eliminates any rolling shutter artifact and works just like a film camera does in terms of exposure.

Are the recommended panning speeds for ALEXA the same as for 35 mm film cameras?

Yes. Our tests comparing film cameras, ALEXAs with an electronic shutter and ALEXAs with a mirror shutter have shown very little difference between them. 

Can I run ALEXA upside down?

Yes, it is no problem to run ALEXA upside down. The fan will still work and cool the camera sufficiently.

The user button function 'Phase sensor' does not seem to work. Why?

The "Phase sensor" user button function is only available with time code set to REC RUN. Setting the time code to FREE RUN or EXT LTC will deactivate the phase function. Also note that you can only adjust the phase of the sensor while the camera is in standby.

Why are the names for framelines, ARRI Look Files or JPEGS sometimes not fully displayed?

A number of files, like frameline files, ARRI Look Files and jpegs, can be freely named when they are created on a computer and copied to the SD card. From a certain length on, they cannot be shown in full on the ALEXA display. This is not pretty but does not prevent their use at all. We recommend to keep the names short and succinct. 

Is it a problem flying in an airplane with a digital camera?

With the kind permission of The Film & Digital Times, here is the answer from Stephen Stough, Cinematographer, Producer, and President of Tradecraft Films, regarding sensors at high altitude, and the perils of shipping digital cameras by air.
"“In general, a short exposure of camera equipment at altitude within the atmosphere is not going to cause any measurable damage, even when powered on, but much less so if powered off in transit. It is true that heavy particles, such as heavy (fast) protons will leave tracks up to 1 mm long through glass, and eventually glass will turn translucent, metals become embrittled and so forth. But, that takes tens of years in space, and probably hundreds of years at the altitudes at which aircraft fly.
It is always possible that a heavy ionization track will damage the insulator(oxide) at a pixel site to the degree that when the sensor is powered on, the resulting short circuit current would flood that pixel site, and burn it out. The possibility isn’t zero. It would take some time to calculate the possibility in a real situation (where the sensor is buried inside an airframe inside a shipping case and inside a camera). If it were my camera, I wouldn’t give it a second thought because I think the possibility in a few hundred hours of aircraft flight to be vanishingly small and economically not worth worrying about. That is, the cost of taking extra protective measures would probably never pay off in terms of an actual lost-pixel event being avoided.”"

Can I use one of the older ARRI work lights on ALEXA?

Yes. The 435 work light can be attached to the ALEXA rosette on the right side and plugged into the RS connector. 

6. MONITORING
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Has the MON OUT output the same image quality as REC OUT?

Yes, the MON OUT output has the same image quality as the two REC OUT outputs. However, there are a couple of differences and extra options that you should be aware of:
MON OUT does not have all the signal formatting options that REC OUT has; MON OUT runs only at 4:2:2 (single link 1.5G) @ 23.976, 24, 25, 29.97 and 30 fps. Second, on MON OUT you can superimpose frame lines and camera information, and shrink the image (surround view) to see more than what will be recorded. These are all features that are useful for monitoring the image, but that you most likely will not want on a master tape. Thus they are only available in the viewfinder and on the MON OUT output, but not on the REC OUT output. So, if all you want is 4:2:2 and you turn frame lines, camera info and surround view off, the signal from MON OUT has the same quality as a 4:2:2 signal from REC OUT.

Should I use progressive (p) or progressive segmented frame (psf) for my MON OUT?

The ALEXA REC OUT and MON OUT scan format can be set to progressive (p) or progressive segmented frames (psf). Progressive outputs a whole frame, while psf splits the frame into two segments, mimicking the output format of interlaced images. Progressive mode looks better and has less delay than psf, so if it works it is to be preferred. Psf enables compatibility to devices that only understand interlaced signals for certain frame rates; some monitors or video transmitters work better with psf, which is why that option exists. You will have to test your monitors and video transmitters to see what works best.

Note that the scan format setting is only for REC OUT and MON OUT and has no influence on the ALEXA internal recording, which is always progressive.

What is the delay of the MON OUT and REC OUT outputs?

The processing inside ALEXA takes less than one frame, so the image delay is less than one frame, assuming sensor speed and REC OUT/MON OUT output speed are the same. When using 180º Image Rotation, the delay is one full frame. Please note that monitors tend to add another two to three frames of delay, depending on the monitor manufacturer, model and display options chosen.

What is 'REC OUT = Clean MON OUT'?

In 16:9/HD/regular speed recording mode, ALEXA has two independent HD-SDI outputs: MON OUT and REC OUT. Before SUP 10, various other recording modes (High Speed, 4:3, ProRes 2K or Open Gate) could not support two independent HD-SDI outputs, and so the MON OUT signal came out of MON OUT and also out of REC OUT (here called 'MON OUT clone').

Starting with SUP 10, some of these recording modes now also support a 'Clean MON OUT' signal on the REC OUT connectors, which can have different settings from the regular MON OUT signal. Thus it is again possible to output a clean Log C signal on REC OUT, while viewing a Rec 709 signal with optional status information overlays and an optional ARRI Look File on MON OUT. Please be aware that not all status information and assistive displays (like Peaking, for instance) are available in all recording modes


For a detailed table of REC OUT options click here.

For a detailed table of 'REC OUT = Clean MON OUT' behavior click here.

What do the colors of the false color exposure check mean?

The false color exposure check for the viewfinder and/or MON OUT changes the image to black and white and certain signal levels are indicated by a specific color. 



What is the false color exposure check based on?

The false color exposure check is based on the color processing set for the respective output signal path. So if you have the viewfinder set to Rec 709, the false color exposure check in the viewfinder will be based on the Rec 709 image. If you have the MON OUT at the same time set to Log C, the false color exposure check for MON OUT will be based on Log C. 

Why does Peaking work better on some images than others?

The ALEXA Classic and XT peaking function works only on horizontal structures. If you have an image with many vertical but few horizontal structures, peaking will be less visible. The ALEXA SXT peaking function works on both horizontal and vertical structures, so this is not an issue with the ALEXA SXT anymore.

Image compare does not seem to work. Why?

When one of the anamorphic de- squeeze options or RETURN IN is on, it is not possible to load an image for the compare function. If the camera is instructed to load an image, the 'Loading Image' screen will be visible until any key is pushed. 

7. ELECTRONIC VIEWFINDER
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Is there a way to avoid the stuttering effect in the viewfinder?

Yes. In the camera's menu, go to MONITORING > ELECTRONIC VIEWFINDER and turn 'Smooth mode' to 'on'. Smooth Mode off: A certain amount of stuttering, which can be observed especially during quick pans, is inherent to all low frame rate (i.e. 24 fps) progressive image displays. The sharpness, contrast and relatively large image size of the EVF-1 make this effect even more apparent. The effect is much less noticeable when panning within the normally accepted maximum panning speeds (which is why some operators prefer to leave Smooth Mode off), and when following an object or person in frame. It may also be helpful to note that the effect will generally be much more apparent in the viewfinder than on separate monitors or projection, so represents a 'worst case scenario'.
Smooth Mode on: The sensor will run at twice the set frame rate and the shutter will be at twice the set shutter angle. So if you have the camera set to 24 fps and 180° with Smooth Mode on, the sensor will run at 48 fps and 358° (Yes, it should be 360° but the sensor is only capable of 358°, and our tests have shown that this slight discrepancy does not make a difference). Every frame will be sent to the viewfinder, which makes the image impression in the viewfinder smoother. Only every other frame will be sent to further processing and recording, so you actually only record the 24 fps/180°. This is the reason why Smooth Mode only works up to half the maximum frame rate and half the maximum shutter angle. Smooth Mode also costs about 7W more power.

The viewfinder image is slightly darker in Smooth Mode. Is this normal??

Yes. Switching the EVF to smooth mode results in a slightly darker EVF image. This has no effect on recorded material.

Can the ALEXA viewfinder stretch my anamorphic images to the proper aspect ratio?

Yes. Anamorphic de-squeezing in the electronic viewfinder and on the MON OUT is included in some ALEXA models and available as a software license key for others. It will perform either a 2x or a 1.3x de-squeeze. The ALEXA Studio and ALEXA XT Studio have an optical viewfinder with a 2x de-squeeze element built-in, which can be replaced with an optional 1.3x de-squeeze module. 

Why would I want to use an electronic viewfinder with the ALEXA Studio?

While an optical viewfinder will provide the best viewing experience, there are four situations where an electronic viewfinder or an on-board monitor have advantages. 

 

  • First, the mirror shutter of the ALEXA Studio supports speeds up to 60 fps. If you want to shoot faster in high speed mode, you must switch the mirror shutter off and thus will loose the use of the optical viewfinder. 
  • Second, if an open shutter angle larger than 180º is desired the mirror shutter must be turned off and the electronic rolling shutter must be used instead. 
  • Third, when shooting in extremely dark situations the electronic viewfinder will be able to show a brighter image. 
  • Fourth, when shooting Open gate sensor mode, the optical viewfinder does not cover the entire width of the Open gate sensor area.
Why is there only one end cap on the rods of the Viewfinder Mounting Bracket VMB-3?

The reason for the end cap is to prevent the sled from sliding entirely off the rods. This can be accomplished with only one end cap. Not having two end caps also saves weight and makes it faster to unscrew when you want to flip the sled around.

8. ALEXA STUDIO (Ground Glasses, Mirror Shutter, Optical Viewfinder)
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What kind of ground glasses can I use with the ALEXA Studio?

The physical frames of ALEXA Studio and ALEXA XT Studio ground glasses and frameglow masks are the same as those used in ARRICAM film cameras. However, the actual frameline dimensions are slightly different, so for a perfect alignment of framelines and captured pixels only the ground glasses and frameglow masks from the ALEXA price list should be used. 

I already have a lot of ARRICAM ground glasses. Can I still use them?

The physical dimensions of the ARRICAM and ALEXA Studio/ALEXA XT Studio framelines are slightly different. The difference is enough that we have decided to make specific ALEXA/ALEXA XT Studio ground glasses, but realistically the difference is barely more than the width of the framelines themselves. So in a pinch it is OK to use ARRICAM ground glasses. If you want to look up the difference in frameline dimensions for yourself, take a look at the old Ground Glass Guide and at the latest ALEXA frameline dimensions documents.     

ARRI Film Camera Ground Glass Guide 

ALEXA Recording Areas, Surround Views and Framelines 

Why is there no Studio ground glass for the 1.85:1 aspect ratio?

Since the 1.85:1 markings are very close to the 1.78:1 markings, we have omitted the 1.85:1 marking from all ALEXA Studio/Studio XT ground glasses and frameglow masks. 

What is the difference between 800 and 1200 grit ground glasses?

The grit defines how rough the surface of a ground glass is. The smoother it is, the brighter it is. The rougher it is, the easier it is to judge focus. 800 grit is the standard that we recommend for ALEXA Studio and ALEXA XT Studio and that has been used for decades in our film cameras. 1200 grit (marked with "1200" on the ground glass) is brighter, but it is more difficult to judge focus.

How does a mirror shutter expose an image?

The white paper "ALEXA Studio Electronic and Mirror Shutter" describes the functioning of the ALEXA Studio's mirror shutter and electronic shutter, the resulting consequences for the cinematographer and provides some practical tips to using each shutter mode.

9. WORKFLOW
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What is the difference between Log C and Rec 709?

Aside from the ARRIRAW output, which contains no color processing, ALEXA can output images with two different color processing methods (commonly called 'gamma') applied. Thus ALEXA can provide the appropriate image format for a wide range of workflows from feature films to television.

 

  • Log C is a signal with a wide gamut color space. This option provides great flexibility in color grading, as it preserves the most information in the recorded image. When grading with Log C images, there is more detail in highlights and dark parts of the image, whites don't clip and blacks don't clog up, there is better color separation and it is less likely for black or white images areas to take on a cast when adding a color. For all these reasons it is actually faster for a professional colorist to grade Log C images than Rec 709 images. ALEXA's unequalled dynamic range, low noise floor, accurate color reproduction and ability to preserve even severely over or underexposed image content is the ideal basis for a successful color grading session. However, you should be aware that Log C is an intermediate color format and not designed as a display standard. Viewed on a regular video monitor, Log C images look flat and desaturated. When using Log C images, color grading becomes an obligatory post production step and for proper previewing, creation of dailies or editing proxies it is necessary to use Look Up Tables (LUT) to convert the Log C image to a Rec 709 image. LUTs for ALEXA can be downloaded from here. For any further help with LUTs, contact digitalworkflow@arri.de.
  • Rec 709 is the output format for a traditional television workflow. 'Rec 709' is short for the International Telecommunication Union's ITU-R Recommendation BT.709. Since Rec 709 is the international standard for displaying images on video monitors, Look Up Tables (LUTs) are not necessary to show these images on monitors or to create dailies or editing proxies. Additionally, Rec 709 images can be easily processed by most HD video postproduction gear in real time. While providing somewhat reduced choices in color grading, Rec 709 still maintains ALEXA's wide exposure latitude, cinematic look and natural color rendition and offers the fastest workflow when using an HD video based infrastructure.
Can I use Log C or Rec 709 with ProRes or DNxHD recording?

Yes. However, when using Log C gamma we recommend ProRes 4444, ProRes 4444 XQ or DNxHD 444 for best results. While Rec 709 can be used equally well with all ProRes or DNxHD codecs, Log C can in some situations lead to banding when using codecs with a higher compression ratio. 

Can I create a custom look for my ALEXA images?

Yes. As of Software Update Packet 4.0 it is possible to apply a customized look to all ALEXA outputs (EVF-1, MON OUT, REC OUT and/or internal recording of ProRes or DNxHD) through an ARRI Look File. Look files alter the way the camera image is converted to the Rec 709 video color space. They can be activated to all image paths of the camera that are set to Rec 709. ARRI Look Files are editable XML files that contain a number of parameters including the ASC CDL primitives slope, offset and power.

ARRI Look Files can be created with a free Mac application called the ARRI Look Creator. This application can be downloaded from http://www.arri.com/camera/digital_cameras/tools/arri_look_creator.html.



Once created, ARRI Look Files can be loaded from the SD card and stored in the camera. One look file can be selected at a time. This look file can be applied to the different image paths individually. So it is possible, for instance, to record a clean Log C image onto a SxS PRO card while outputting a Rec 709 image with a look applied on the MON OUT output. As soon as a look file gets applied to any output, the data of the look file is stored in the metadata of ARRIRAW, ProRes or DNxHD clips and embedded in the HD-SDI metadata (for video and ARRIRAW T-Link).

Please note that the ARRI online LUT Generator is not designed for creating ARRI Look Files, but rather for creating Look Up Tables for third party equipment.

Can I combine ALEXA’s Log C with S-Log material?

Yes. It is relatively easy to use a 1D LUT to convert ALEXA's Log C material to S-Log or vice versa. LUTs for ALEXA can be created with the LUT Generator at http://www.arri.com/camera/digital_cameras/tools/lut_generator.html 

Will there be an F-Log, S-Log or P-Log output option for ALEXA?

No. We currently have no plans to incorporate F-Log, S-Log or P-Log. When working in a film-style post workflow, we feel that the Log C output option provides the best results. 

Why does ARRIRAW frame grab not work?

Frame grabs of ARRIRAW files work only on ALEXA Classic cameras in 16:9 mode when REC OUT is set to T-Link. 

What if I need 50i content?

Set ALEXA to 50 fps, and the RECORD OUT to DL 1.5 G. Out of REC OUT 1 you will get a 50i signal. Don't use REC OUT 2. Even though it also outputs a 50i signal, some lines are missing at the beginning and at the end. 

What if I need 720p content?

ALEXA does not produce 720p images. However, shooting 1080p allows you to sell your program to all countries that have chosen 1080p, and it can easily be down-converted to 720p.

10. REMOTE CONTROL
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How can I remotely control ALEXA?

There are five different ways to remotely control an ALEXA camera. 

  • The Remote Control Unit RCU-4 supplies complete cabled remote control of all ALEXA camera models, including the ability to change all settings.

  • All ALEXAs with a Plus right side cover (ALEXA Plus, ALEXA Plus 4:3, ALEXA Studio, ALEXA XT Plus and ALEXA XT Studio) can be wirelessly controlled through the ARRI Wireless Control Unit WCU-4. The WCU-4 connects directly to the camera's radio, so there are no extra boxes or cables.

  • The WCU-4 can also be used with none Plus ALEXA cameras (ALEXA, ALEXA XT, ALEXA M, ALEXA XT M), as long as a Universal Motor Controller UMC-4 is attached to the camera. The WCU-4 communicates with the UMC-4, and the UMC-4 with the camera. 

  • Using the built-in web browser of all ALEXA cameras, any computer can remotely control all camera functions. For this to work, the computer's Ethernet port must be connected to the camera's ETH port.



  • Basic REC/STOP control of all ALEXA cameras can be achieved with the cabled RS-4 switch.



 

 

What settings of ALEXA can I change with the WCU-4?

The WCU-4 can start/stop recording for the ALEXA. For changing camera settings, a remote license key is necessary. 

The ALEXA Remote License Key activates remote camera setup capabilities via WCU-4 for ALEXA Plus, ALEXA Plus 4:3, ALEXA XT Plus, ALEXA Studio, and ALEXA XT Studio cameras. The ALEXA Remote option can be activated and de-activated by loading or deleting the license file on the WCU-4. Requirement is WCU-4 Software Update Package 01.00.00 or higher and ALEXA Software Update Package 8.0 or higher.

With the Remote License Key activated, the WCU-4 can change the following parameters:

 

  • Sensor Frame Rate
  • Shutter Angle
  • Exposure Index
  • White Balance
  • ND Filter (ALEXA Studio)
  • Peaking on Monitor Output (on/off)
  • Surround View on Monitor Output (on/off)
  • False Color on Monitor Output (on/off)
  • Status Info on Monitor Output (on/off)
  • Frame Lines on Monitor Output (on/off)
  • User Buttons 1-3 (with WCU-4 SUP 2 and ALEXA SUP 11 onwards)
Does the RCU-4 work with the ALEXA M?

Yes. However, the RCU-4 has to be connected to the ALEXA M or ALEXA XT M Ethernet connector on the rear of the camera body. When connected to the ETH connector on the camera head, it will not work.

Are there any limitations when using the Remote Switch RS-4?

Yes. The RUN LED on an RS-4 only works up to about 340 degrees shutter angle. This is because the RS-4 was originally built for film cameras, which never had such wide shutter angles. Also note that on the RS-4, a red LED means "not yet recording/stopping" and a green LED means "recording".

What are the best browsers to use with ALEXA's remote control web browser?

Our tests have shown best results with Firefox, Chrome and Safari. Internet Explorer is not compatible with some of the Web 2.0 technologies used in the ALEXA web bowser. 

Why does ALEXA's remote control web browser not work?

It is possible that the NETWORK ACCESS has been set to READ ONLY. Check in MENU > SYSTEM > NETWORK ACCESS READ-ONLY to make sure it is OFF when you want to use the remote control web browser function. 

11. HEAT/COLD/ENVIRONMENTAL
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What is the High Humidity sensor temperature? Will it make the camera quieter?

The temperature of ALEXA's sensor is being actively maintained at a constant 35 degrees Celsius. When shooting in very hot and humid conditions, in rare cases it is possible for condensation to build on the inside of the filter pack in front of the sensor. In this case the sensor can be switched to 'High Humidity' in the SYSTEM > SENSOR > SENSOR TEMPERATURE menu, which will heat the sensor to 40 degrees. Running the sensor at 40 degrees will only affect condensation. It will not affect the image quality during normal operation, nor will it increase or reduce the camera's sound. However, since it uses more power we recommend to run the sensor at its standard temperature mode by default. High Humidity mode will be indicated by a palm tree icon in the camera right display, and by the 'i' information icon in the viewfinder. 

If you are shooting in very hot temperatures and have trouble with fan noise, switch the camera into 'Rec Low' mode in the SYSTEM > FAN MODE menu. When the fan is set to Rec Low, it will run at a high rate when the camera is in Standby, and run at a low rate when the camera is recording. 

Why does the ALEXA at first show the sensor to be too hot when started in very cold temperatures?

When an ALEXA is powered up in very cold temperatures the sensor temperature regulating circuit can take a couple of minutes to settle on the proper temperature. During that time you might get warnings that the sensor is too hot. In cold temperatures it is always recommended to let the camera come up to a proper working temperature for a couple of minutes before recording.

What should I consider when shooting in extremely hot temperatures?

In most cases, the camera should be run in 'Regular' fan mode, which achieves silent running at temperatures of up to +30 degrees Celsius (+86 degrees Fahrenheit). This has proven sufficient for most shooting situations. Once the ambient temperature, and thus the camera's internal temperature, increases, the camera will slowly increase the fan speed, and thus fan noise, to assure proper cooling of the electronics. This works the same in all operating modes: Standby, Record and Playback.

In the rare case that fan noise becomes objectionable because of higher ambient temperatures, it is possible to switch the fan into 'Rec low' mode. As long as the ambient temperature remains below +30 degrees Celsius (+86 degrees Fahrenheit), 'Rec Low' mode is no different from 'Regular' mode. However, once the camera's internal temperature reaches a certain threshold (which is not directly related to ambient temperature, but approximately around an ambient +30 degrees Celsius (+86 degrees Fahrenheit), the fan will run fast during Standby and Playback to pre-cool the camera, and will run slowly and silently during recording for as long as possible.
Additionally, when the camera is set to 'Rec low' fan mode it will allow a higher internal temperature in order to stretch the silent running as long as possible, which means that the camera housing can be warmer to the touch than in 'Regular' mode. Since 'Rec Low' increases the camera's noise in hot environments during Standby and Playback, we recommend 'Rec low' mode only when the fan noise becomes objectionable in very hot ambient temperatures.

In the unlikely case that the camera reaches its temperature limit while recording, it will slowly start increasing the fan speed to cool its electronics.
 

 

Note: noise can also be caused by a worn out fan. In that case, replace the fan.

What should I consider when shooting in extremely cold temperatures?

While ALEXA is officially rated to -20° C / -4° F (@ 95% humidity max, non condensing), we have had a number of customers who have worked with ALEXA at significantly lower temperatures, without any heating barneys and without any problems. However, below -20° C / -4° F any humidity in the air or from the human breath will quickly condense on the eyepiece and even freeze there, obscuring the view, so an eyepiece heater is recommended. The ARRI Heated Eyecups HE-6 or HE-7 work well with the ALEXA eyepiece, while the older heated eyepieces designed for film cameras do not.

Also, keeping batteries warm and charged is critical, as batteries loose their power at cold temperatures.

12. SxS PRO and SxS PRO+ Cards
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Which Types of SxS cards does ALEXA support?

ALEXA cameras up to SUP 9.0 support SONY SxS PRO cards. From SUP 10 on, ALEXA cameras support SxS PRO and SxS PRO+ (first generation) cards. As of SUP 11, ALEXA cameras support SxS PRO and both first and second generation SxS PRO+ cards.

ALEXA does not support SONY SxS-1 cards, third party SxS cards, the SONY MEAD-MS01 Memory Stick Adaptor or third party adapters.

ALEXA XT cameras and ALEXA Classic cameras with the XR Module upgrade need the SxS Adapter to use SxS PRO or SxS PRO+ cards.

How accurate is the remaining time display for SxS PRO/SxS PRO+ cards?

The time displayed by ALEXA is based on the maximum possible data rate for a given codec at a given frame rate. Since the Apple ProRes codecs are variable bit rate codecs, the remaining time depends on image content, and will usually be longer than the time indicated. Please note that the estimation is updated in short intervals and the closer the card gets to be full the more accurate the estimation will be.

How can I switch to the other SxS PRO/SxS PRO+ card when an ALEXA Classic is inaccessible?

If you don't have a RCU-4 or WCU-4, record on card 1 until it is full. When the card is full, ALEXA will stop recording. When you then press REC again, the camera will automatically start recording onto the second card. If the second card then also fills up, ALEXA is smart enough to NOT switch back to card 1, so you have to exchange cards.
If you do have a RCU-4 or WCU-4, you can switch which card you record to by assigning one of the USER buttons to the 'Toggle SxS' command.

Can I use a SxS PRO/SxS PRO+ card that has been formatted with a previous camera software?

No. You should only use cards that have been formatted with the same camera software version as the camera has you will be using. 

Why does recording to SxS PRO+ cards start slower?

When the REC button is pushed to start recording, it takes minimally longer until the recording starts when suing SxS PRO+ cards. This is due to the new architecture of these cards.

13. QUICKTIME/PRORES
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I interrupted a ProRes/SxS recording. What now?

If a recording has been interrupted, for instance by a power cut or by removing the card without stopping the recording, the content of the card is readable, but the file system may have been compromised. Copy the card's content to some other media and reformatted the card before recording onto it again.

Should I shoot ProRes HD or ProRes 2K?

For an HD deliverable, ProRes HD is best. Shooting ProRes 2K and down sampling to HD in post will not get you any resolution advantage, on the contrary, it may look worse than shooting ProRes HD in-camera. However, if you need to do some reframing, resizing, rotating or stabilizing in post, you could shoot ProRes 2K and then crop in post to HD. For that you would have to create some custom frameline so you see the original HD inside the 2K frame. While the ProRes 2K and the HD use a slightly different downscale factor inside the camera, we have conducted extensive tests that showed neither a difference in MTF nor a visible difference between shooting HD and shooting 2K with a crop to HD.
For a theatrical 2K deliverable, ProRes 2K is best as it is designed for a 2K cine post workflow.

When I change camera settings during recording, what will the FCP XML file record??

The FCP XML file on the SxS cards will record the camera settings at the beginning of a clip. If, for instance, the EI is changed from 400 to 800 while the camera is recording, the FCP XML text for this clip will only show the EI 400 value.

Why is the photo site count for ProRes 2K 4:3 (2868 x 2150) different from ARRIRAW 4:3 (2880 x 2160)?

While keeping the ProRes 2K 4:3 photo site count the same as ARRIRAW would have been simpler for all involved, our paramount concern is image quality. In an ironic turn of digital image making, it turns out that by reducing the image width from 2880 photo sites to 2868, we can use a much better downscaling algorithm in the camera and produce a better looking image. 

Why are there four fours in the 'ProRes 4444' name?

The official Apple name of this codec is 'ProRes 4444', pronounced "ProRes four by four". Three fours represent the three color channels, while the fourth four stands for an alpha channel. The alpha channel can be used in post but has no relevance for image capture. 

Why is ProRes always set to legal range?

Apple specifies that ProRes should be legal range. Our tests have shown that an extended range ProRes file can result in clipping in some Apple programs. However, the difference between legal and extended coding are essentially academic, and will not have any effect on any real world images. An image encoded in 10 bit legal range has a code value range from 64 to 940 (876 code values), and a 10 bit extended range signal has a code value range from 4 to 1019 (1015 code values). Contrary to popular belief, extended range encoding does not provide a higher dynamic range. It is only the quantization (the number of lightness steps between the darkest and brightest image parts) that is increased by a marginal amount (about 0.2 bits).

Why does Final Cut Pro warn that an ALEXA ProRes file is not optimized for real-time playback?

If a QuickTime clip that uses the ProRes codec begins with dark frames, FCP may display a warning dialog saying that the clip is not optimized for real-time playback. This is a false warning that can occur with any ProRes clip, not just those from ALEXA. 

14. PRORES 4444 XQ
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What is the advantage of ProRes 4444 XQ?

ProRes 4444 XQ, available as part of SUP 10, has a lower compression ratio (about 1:4.5) than ProRes 4444 (about 1:6.8). This means a higher data rate, which is great for doing extreme color grading in post. The fact that it is a 12 bit codec (like ProRes 4444) also helps in preserving the superior tonal range of ALEXA's Log C signal. 

Who will use ProRes 4444 XQ?

ProRes 4444 XQ is one more choice available in addition to the other ProRes codecs, ARRIRAW and DNxHD. Customers can choose the recording format that best matches their post workflow, distribution format and budget. This flexibility has always been one of the great advantages of ALEXA cameras. While we expect ProRes 4444 to continue to be the most popular recording format for ALEXA shows, we think that a number of commercials and high end TV shows will want to use ProRes 4444 XQ. 

Which ALEXA models will support ProRes 4444 XQ ?

ProRes 4444 XQ will work on all ALEXA XT cameras and all ALEXA Classic cameras with the XR Module upgrade. The reason is that the XR/XT cameras have a much more powerful compression board than the ALEXA Classic cameras. The compression board of ALEXA Classic cameras cannot handle the higher data rate of ProRes 4444 XQ. 

Will ProRes 4444 XQ work with ProRes HD, 2K, 16:9 and 4:3?

Yes, all currently supported ProRes resolutions (ProRes HD and ProRes 2K) and all supported aspect ratios (ProRes HD 16:9, ProRes 2K 16:9 and ProRes 2K 4:3) can take advantage of ProRes 4444 XQ. 

What recording medium can I use to record ProRes 4444 XQ with?

You can use SxS PRO cards, SxS PRO+ cards, CFast 2.0 cards or XR Capture Drives.

Which post software supports ProRes 4444 XQ?

Currently, ProRes 4444 XQ is supported by:

 

  • Final Cut Pro X 10.1.2 and later
  • BMD Resolve 11 Beta 2 and later (Mac and Linux)
  • Colorfront ExD 2014 and OSD 2014 and later
  • Quantel Pablo Rio
  • Pomfort Silverstack
  • Avid Media Composer (8.1 and higher)
  • Autodesk Smoke, Flame, assist, Flare, Lustre
  • Codex Vault
  • Filmlight Baselight
  • Filmlight Daylight

 

Many other applications running under the latest Apple Mac OS with the latest QuickTime version installed.

Please check with your post production house before you shoot with ProRes 4444 XQ to make sure that their tools support ProRes 4444 XQ. 

What are the maximum frame rates for ProRes 4444 XQ?

See tables below.

For a detailed table of frame rates for ALEXA XT cameras click here.

For a detailed table of frame rates for ALEXA cameras with the XR Module Upgrade click here

What is the data rate for ProRes 4444 XQ?

See table below. For comparison: ProRes 4444 HD/16:9 at 29.97 fps is about 330 Mbit/s, while ProRes 4444 XQ HD/16:9 at 29.97 fps is 495 Mbit/s. Thus the ProRes 4444 XQ data rate is 1.5x higher than the data rate of ProRes 4444.

For a detailed table of data rates for ALEXA XT cameras and ALEXA Classic cameras with the XR Module upgrade click here

Does this mean that I need more storage capacity when I shoot ProRes 4444 XQ?

Yes. Since ProRes 4444 XQ has about 1.5x the data rate of ProRes 4444, you will need about 1.5x the storage capacity. In exchange you get a higher quality image. 

Will AMIRA also support ProRes 4444 XQ?

That's possible in the future but at this stage ProRes 4444 XQ will only be available for ALEXA XT/XR cameras.

15. DNXHD
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Why does the camera sometimes switch back into ProRes mode?

If the internal recording is set to DNxHD, the camera will switch to a ProRes codec when you enter a mode that is not available with DNxHD (e.g. 4:3 sensor mode). Please check your camera setup when changing normal/high speed and sensor mode. 

Why does ALEXA MXF/DNxHD use OP1a?

OP1a is more suited for recording a stream of data in a digital camera than OP-Atom. Aside from a number of technical reasons, an interruption of the recording in OP1a will result in just a few lost frames, while in OP-Atom the whole clip would be lost.

In addition, many broadcasters rely on MXF/OP1a files as their primary acquisition and archiving format. Being able to deliver this straight out of the camera has a lot of potential in terms of cost-savings. As soon as material has been transferred from the camera, the clips can be tagged for the Media Asset Management Database and sent straight to the archive.

Can I convert ALEXA DNxHD OP1a to OP-Atom?

When working with Avid Interplay, the use of OP-Atom is mandatory, as the indexing service that maintains the database will only accept media in this format. If, however, several editors will work on the material simultaneously, or if the amount of clips that will be accessed for editing were to exceed several thousands of clips, it is recommended to convert the material into OP-Atom MXF files.

Converting the MXF container format does not require transcoding of the ALEXA material. The essence streams only need to be consolidated, i.e. separated and re-wrapped into individual files. The speed of this process greatly depends on the speed of the interface and storage used to read/write the media files.

16. PLAYBACK
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Why does my ProRes footage not play back?

It is possible that the footage was recorded with an older or newer version of the ALEXA Software Update Packet (SUP) that is installed on the camera you are using for playback. The INFO screen will report: "files not consistent". ALEXA can only play back footage recorded with the same SUP version in-camera. 

I see an artifact in playback of 4:3 High Speed footage. Is that normal?

Yes. During playback of material shot in 4:3 above 48 fps, a thin line can be observed on the edge of the image. This is a playback artifact that is not in the recorded image. 

I see a black border in playback of 16:9 ARRIRAW footage. Is that normal?

Yes. During playback of 16:9 ARRIRAW footage, a dark border of 1 pixel width is visible at the edges of the image. This is normal and the recorded image is not affected.

Why does the sensor not switch to the set frame rate when I press LIVE during playback?

When pressing the LIVE button in the PLAY screen the HD outputs show the live image from the sensor, however the sensor does not run at the frame rate selected in the home screen but at the project frame rate. This is a result of the way the ALEXA electronics work, and is only noticeable when the sensor is set to a different frame rate than the HD outputs.

Can I view ALEXA ProRes clips on an AJA Ki Pro?

ProRes QuickTime files recorded by ALEXA do not show up on a Ki Pro if copied directly from SxS PRO card to the Ki Pro's hard drive. After re-saving the files from another program such as Final Cut Pro (FCP) the clips can be played back on the Ki Pro. 

17. AUDIO
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Is ALEXA’s audio compressed?

No, since audio has such low data rates in comparison to images, it is recorded uncompressed onto all the in-camera recording media and embedded uncompressed into the HD-SDI data stream. 

18. SYNC AND 3D QUESTIONS
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Can I sync the ALEXA Studio to the other ALEXA cameras?

The ALEXA Studio can be synched to the other ALEXA cameras as long as its mirror shutter is off. Sync is not possible with the ALEXA Studio while the mirror shutter is on. 

What are ALEXA’s advantages for 3D shoots?

Integrating the ALEXA M and ALEXA XT M is the best way to handle 3D rigs. While the camera head is lightweight and small, all magazine changes and camera settings can be performed on the body, which can be located at the DIT station.

In addition, the high base sensitivity of ALEXA helps with 3D mirror rigs, as the mirror always takes some of the light. The wide exposure latitude helps to convey a more realistic and natural image, as clipping artifacts can be very detrimental to the viewer's stereoscopic impression. The physical relationship of sensor position to camera mounting points is exactly the same on every ALEXA, making it easy to integrate ALEXAs into 3D rigs and assuring an easy replacement of one ALEXA for another on 3D rigs. Cinematographers and high-end 3D solution providers have confirmed, from personal experience on ALEXA 3D projects, that the quality of 3D footage captured by ALEXA is simply stunning. From Software Update Packet 2.1 on, ALEXA has been capable of precise 3D synchronization of sensor, HD output, timecode and camera settings. To use these features, the ALEXA 3D Cable Set (K0.71032.0) is necessary.

Will playback on two ALEXAs in 3D sync also play back in sync?

No. 3D Sync is only for record mode, it does not apply in playback. 

Can I use Lens Sync with an ALEXA and an ALEXA Plus?

No. Lens sync only works with two Plus cameras, not with none Plus cameras. 

I am trying to Sync two ALEXAS at 0.75 fps and it does not work. Why?

The sensors of two cameras can only be synchronized via an EXT sync cable at or above 1fps. Since 0.75 is exactly 5 stops under 24 fps, we decided to supply the frame rate anyway. 

Is there anything to pay attention to when using 3D lens sync?

Yes. When using two lenses on two ALEXA Plus cameras with 3D sync and 3D lens sync (i.e. the ARRI WCU-4 or cmotion cvolution system is used to control the Master lens while the Slave lens follows), the lens with the larger focus read out at its mechanical close focus end stop must be on the Master camera. 

In order to find out which lens has the larger focus read out:

 

  • Place each lens on an ALEXA Plus and look at the focus value on the LDS screen of the cameras display (WRS button > LENS DATA). 
  • Turn the lens to its mechanical close focus end stop. Note the number that is displayed for focus. 
  • The lens with the larger number must be on the Master camera. 
  • If the lenses are reversed it is possible for the Master lens to reach a close focus value that the Slave lens cannot reach, and thus the Slave lens would be out of focus as long as the master is in that range. 
19. ACCESSORIES
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What kind of bridge plates can I use with ALEXA cameras (except Studio and XT Studio)?

There are three different methods to attach ALEXA cameras (except Studio and XT Studio) to a bridge plate. 

 

  • 1. Each ALEXA comes with a Wedge Adapter WA-1 attached to the bottom of the front foot. This allows the camera to be attached to an ARRI, SONY or Panasonic video-style quick release plate, and is a great choice for those who already own video-style quick release plates. 
  • 2. Those who have a rental house full of traditional ARRI bridge plates can replace the WA-1 with the Bridge Plate Adapter BPA-1 or BPA-2. With the BPA-1 or BPA-2 attached, the camera can be attached to the Bridge Plates BP-3, 5, 8 or 9.
  • 3. If you have neither traditional ARRI bridge plates nor video-style quick release plates, you can equip ALEXA with the new Bridge Plate BP-12 (for 19 mm studio support rods) or BP-13 (for 15 mm studio support rods) built specifically for ALEXA. The BP-12 and BP-13 fulfill the same function as the BP-3, 5, 8 or 9. Please note that BP-12 and BP-13 are not compatible with the old style bottom plates with the thinner, spring loaded pin. They are compatible with the new bottom plates with the wider pin. 

 

What kind of bridge plate can I use with ALEXA Studio and ALEXA XT Studio?

Since the front foot of ALEXA Studio and ALEXA XT Studio is larger than that of the other ALEXA cameras, a standard BP-8 (for 19 mm studio support rods) or BP-9 (for 15 mm studio support rods) can be used. For the same reason, the ALEXA Studio and ALEXA XT Studio are not compatible with the Wedge Adapter WA-1, Bridge Plate Adapter BAP-1 or BPA-2 or any an ARRI, SONY or Panasonic video-style quick release plate. 

Which ARRI accessories for hand held can I use with ALEXA?

For the most lightweight setup, attach a left and right side handgrip to the two rosettes on ALEXA’s left and right side and use the lightweight rods for matte box and follow focus. For a wider stance, use the "Extension for Handgrip" accessory (K2.47136.0) to move one or both hand grips further away from the camera. For more comfort, use ALEXA’s shoulder pad, the SP-4. If you don’t mind a little more weight, you can attach the Bridge Plate BP-12 to ALEXA, and then attach the shoulder set S-4 or S-5 to the BP-12, which gives you more options in positioning the hand grips. 

We now offer the ALEXA Handgrip Set (K0.71033.0) which contains two handgrips, two extension tubes to extend the handgrips further left and right and two extensions to place the handgrips further in front of you. 

For further options regarding Professional Camera Accessories, please have a look at our Suggested Kits for ALEXA

What is the difference between the ALEXA Shoulder Pads SP-3 and SP-4??

The SP-4 is slightly shorter, and thus also fits with the Bridge Plate BP-12 as well as with ALEXA Studio or ALEXA XT Studio in combination with BP-8. 

Are ALEXA’s 15 mm lightweight rod receptacles in the same position as on 416 and 16SR cameras?

Yes. Diameter, distance to each other and to the optical lens axis of ALEXA's built-in lightweight rod receptacles are exactly the same as those of the 416 and 16SR series of cameras. So all the lightweight rod accessories that have been used with the 416 and 16SR series of cameras can also be used with ALEXA. 

Do you sell ALEXA Timecode cables?

No. There are various third party companies that sell timecode cables for ALEXA (including Ambient), and many sound persons make their own. The wiring diagram for the ALEXA TC connector can be found in the back of the ALEXA manual, which can be found on the DOWNLOADS web page

What is the Handle Extension Bracket HEB-2 for?

As the name implies, this bracket can be used to extend the length of ALEXA's handles. In addition, it has a built-in tape hook. When the HEB-2 is attached to the front of ALEXA's Center Camera Handle CCH-1 with the tape hook facing upwards, this tape hook allows the assistant to attach the measurement tape to a point that is as high as possible to clear the matte box. The HEB-2 can also be attached to any other 3/8-16 UNC threaded mounting point. Please note that we also have a HEB-1, which is a slightly shorter version without the tape hook. 





What is the Leveling Block LB-1 for?

When ALEXA (except ALEXA Studio and ALEXA XT Studio) is equipped with a bridge plate and an on-board battery, and the camera is placed on a flat surface like a table or the ground, the camera will rest on the bridge plate and the battery. Since this is not optimal for the camera/battery interface, the LB-1 can be attached to the back foot of ALEXA's shoulder arch. Then ALEXA will rest on the bridge plate and on the LB-1. 

Is it OK to cover ALEXA when it is raining?

ALEXA needs air in order for the cooling fan to work properly. Placing a plastic bag or fully enclosed rain cover over ALEXA will cut off the air supply to the cooling system. While this is OK for short periods of time, doing it for extended periods of time is not recommended. ARRI offers a special rain cover (ALEXA Rain Protector ARP-1, K2.72026.0) that has special vents built in for this reason. 

Is it OK to use ALEXA in an underwater housing?

Yes. We have run various thermal simulations and talked to numerous underwater cinematographers and found that with both aluminum and fiber glass underwater housings the cooling effect of the water is in most cases sufficient to keep ALEXA at the proper temperature. We advise to switch the sensor to the 'High Humidity' mode. This will run the sensor a little hotter, requiring less cooling, with no negative effects on image quality. This prevents condensation on the sensor.


20. SENSOR/IMAGE PROCESSING
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Is there a low contrast filter in front of the ALEXA sensor?

No. In front of the ALEXA sensor is a cover glass, an infrared filter (IR), an optical low pass filter (OLPF) and a filter for ultraviolet light (UV). All these components are of the highest optical quality (and thus not inexpensive) to assure the best possible overall image quality at this critical point in the image path. 

What is the difference between photosites and pixels?

Sensors have photosites, files have pixels. The word ‘pixel’ is a contraction of the term ‘picture element’, and the light sensitive areas on a sensor are not picture elements yet.

What are the photo site dimensions of the ALEXA sensor?

There are three different versions of the ALEXA ALEV 3 Sensor. Please note that it is not possible to upgrade from one sensor version to another. 

 

  • The 'ALEV 3 16:9' is used in the ALEXA, ALEXA Plus, ALEXA HD and ALEXA HD Plus cameras. This sensor has a total of 2880 x 1620 photo sites that can be used for generating an image to be recorded. A larger sensor area (3168 x 1782) is used for surround view.

    For a drawing with details about the 'ALEV 3 16:9' recording areas, surround views and framelines click here.

  • The 'ALEV 3 16:9/4:3' is used in the ALEXA Plus 4:3, ALEXA M and ALEXA Studio cameras. This sensor has a total of 2880 x 2160 photo sites that can be used for generating an image that can be recorded. A larger sensor area (3168 x 2160) is used for surround view.

  • The 'ALEV 3 16:9/4:3/Open Gate' is used in the ALEXA XT, ALEXA XT Plus, ALEXA XT M and ALEXA XT Studio. This sensor has a total of 3414 x 2198 photo sites that can be used for generating an image. In 16:9 and 4:3 modes a larger area is used for surround view, but in Open Gate mode there is no surround view as all available photo sites are used to generate an image.

    For a drawing with details about the recording areas, surround views and framelines, page 1 of 2 click here.

    For a drawing with details about the recording areas, surround views and framelines, page 2 of 2 click here.
What are the differences between the sensor modes 16:9, 4:3 and Open Gate?




16:9 Sensor Mode
For ProRes, DNxHD recording as well as HD-SDI outputs 2880 x 1620 photo sites are read from the sensor. This data is then debayered and downscaled in camera by a factor of 1.5, leading to a beautiful 1920 x 1080 image. 


For ARRIRAW the same 2880 x 1620 area is read, but that image data is neither debayered nor downscaled in the camera. Instead, it can be debayered in post with a number of optional scaling factors for anything from an HD to a 4K output image. 


Both the electronic viewfinder and the HD-SDI MON OUT output can be put into surround view mode, where more is shown than the area recorded. In that case they display an area that covers 3168 x 1782 photo sites from the sensor, which is 5% more on each side than the recorded 2880 x 1620. 

4:3 Sensor Mode
The 4:3 sensor area is taller than the 16:9 sensor area (2880 x 2160), but not wider. Distribution formats that are limited by the sensor's width (1.78:1, 1.85:1, 2.39:1 flat and 2.39:1 with 1.3x anamorphic squeeze) do not gain resolution by using 4:3 sensor mode. However, in 4:3 sensor mode those formats gain the option for significant vertical repositioning. The one format that gains significant resolution in 4:3 sensor mode is 2.39:1 with 2x anamorphic squeeze (traditional CinemaScope). 

ProRes 2K 4:3 captures 2868 x 2150 photo sites from the sensor. The image data is debayered and downscaled in camera to 2048 x 1536. 

For ARRIRAW 4:3 a 2880 x 2160 area area is read. That image data is neither debayered nor downscaled in camera. Instead, it can be debayered in post with a number of optional scaling factors for anything from an HD to a 4K output image.  

Both the electronic viewfinder and the HD-SDI MON OUT output will use a 2880 x 2160 area (4:3) from the sensor, debayer and downscaled it in camera by a factor of 1.5 and display it as a pillar box image. 

Pillar box means a 4:3 image with two vertical black bars ("pillars") within the 16:9 HD image

Both the electronic viewfinder and the HD-SDI MON OUT output can be put into surround view mode, where more is shown to the left and right than the area recorded. Unfortunately no surround view above and below the recorded image can be shown. In that case they display an area that covers 3168 x 2160 photo sites from the sensor, which is 5% more left and right than the recorded 2880 x 2160. 


The optical viewfinder of ALEXA Studio and ALEXA XT Studio have about the same width as the surround view in the electronic viewfinder, but it shows more on top and bottom, so when using 4:3 mode, the optical viewfinder can show a proper surround view all around. 

Open Gate Sensor Mode
In Open Gate sensor mode the whole area of the sensor (3414 x 2198) is captured. This is great for a 4K release or for gaining more resolution for repositioning, resizing, rotating or stabilizing in post. Open Gate is only available in ARRIRAW. Surround view is not available in Open Gate mode, as we are already using all photo sites for the recorded image. The image will be displayed in the electronic viewfinder and on the MON OUT output in pillar box format.

Please note that the optical viewfinder of the ALEXA Studio and ALEXA XT Studio cannot show the entire width of the Open Gate image. We recommend to use MON OUT as a reference or use the EVF-1 for exact framing.




How many code values are there per stop in ALEXA’s Log C signal?

When the ALEXA Log C signal is recorded as 10 bit video, you will have approximately 80 code values in each stop above 18% grey. The original Cineon log encoding is based on the density of color negative having a gamma of 0.6. This results in 90 code values per stop. The large dynamic range of the ALEXA camera makes it necessary to use a lower gamma value. Modern color negatives, having more latitude than negatives 15 years ago, also have a gamma lower than 0.6.

At which signal level is an 18% grey card in ALEXA’s Log C signal?

The nominal value for a grey card exposed according to a light meter is 39% in the Log C video signal, which is the number 400 in the 10 bit encoding. Bear in mind that tolerances in meters and lenses may give you slightly different results.

At which signal level is an 18% grey card in ALEXA’s Rec 709 video signal?

The nominal value for a grey card exposed according to a light meter is 38% in the Rec 709 video signal. Note that in a video signal you don't have an equal amount of code values in each stop. Therefore, there is no easy formula telling you where, for example, 2 stops over or under are placed. The following values may be used as a guideline:

The values will vary a little bit (by 1-3%) with the exposure index. Also, bear in mind that tolerances in light meters and lenses may give you slightly different results.

Which code values does ALEXA use for legal and extended range HD video on the HD-SDI outputs?

According to SMPTE 274M 8.7, the following code values can be used for legal range HD video in 10 bit systems: 64-940 for RGB and Y and 64-960 for Cb and Cr. ALEXA complies with the code value ranges as defined in this standard.

According to SMPTE 274M 8.12, the following code values can be used for extended range (called undershoot/overshoot in SMPTE 274M 8.12) HD video in 10-bit systems: 4-1019 for RGB and YCbCr. ALEXA makes use of the full 4-1019 code values for extended range, just like the D-21.

21. SERVICE
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How can I find an ARRI service center?

Look at our service contacts web page 

How do I update the ALEXA software?

You first have to register your ALEXA camera by serial number to download Software Update Packets (SUP). SUPs can then be uploaded to the camera either from an SD card, or from a computer via the ALEXA Ethernet/RJ-45 Cable KC 153-S (3.00m/9.8ft, K2.72021.0).

If you have not registered yet, go to the ALEXA DOWNLOAD web page. When the page loads there will be a selection of downloads. Please go to the section of the latest ALEXA Software Update Packet and click on 'Please -> register to get an account.' The ALEXA customer registration page will be opened.

Can I return to an old software version after I have upgraded my ALEXA with new software?

This is possible with some Software Update Packets but not with others. Take a look at the detailed notes in the release notes that accompany each SUP and can be found on the ALEXA DOWNLOAD pages.

Can I use a User Setup file from a previous software version?

Unfortunately, no. User Setup files cannot be used across Software Update Packets (SUPs), i.e. a User Setup file created with SUP 9 is not compatible with SUP 10. 

Where can I find pin-outs for ALEXA connectors?

The ALEXA Manual has an appendix that shows the pin-outs for ALEXA connectors. You can download the manual here