ALEXA SXT Frequently Asked Questions

Welcome to the frequently asked questions about ALEXA SXT.
If you have a question not listed here, please use the ARRI Forum or send an email to to fmerten@arri.de.
Version: February 3, 2017.

1. ALEXA Camera Line-up and Upgrades
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What are the changes to the ALEXA camera line-up?
  • ALEXA SXT EV, ALEXA SXT Plus and ALEXA SXT Studio replace the ALEXA XT cameras. 
  • Due to the launch of ALEXA Mini, there will not be an ALEXA SXT M. 
  • The original ALEXA remains in the program and gets re-named 'ALEXA Classic EV'. 
  • The ALEXA Plus upgrades (ALEXA to ALEXA Plus and ALEXA XT to ALEXA XT Plus) are discontinued because of declining demand. However, there is still an ALEXA SXT EV to ALEXA SXT Plus upgrade.

What are the hardware and software differences between ALEXA XT and SXT cameras?

In terms of hardware, the main electronics boards in ALEXA SXT cameras are new. These are the same high performance electronics boards as used in the ALEXA 65. Additionally, the left side cover containing the media bay is new. What has remained is the sensor: ALEXA SXT cameras have exactly the same sensor as the previous generations of ALEXA cameras, the 3.4K ALEV 3 sensor, that is the basis for the image quality of all ARRI digital cameras. 

In terms of software, the new image processing path and the pixel correction algorithm from the ALEXA 65 are being used, as well as color management and noise reduction from AMIRA. 

What can the SXT do that the XT or the ALEXA Mini cannot do?

Click image to enlarge

What upgrades are available for ALEXA cameras?

Here is an overview of all available ALEXA upgrades:

What is the difference between the SXT Upgrade 13/14 and the SXT Upgrade 15/16?

It is our philosophy to make sure that our customers have a functioning business model, so we try to make sure that those who recently bought a camera are not left in the dust. For ALEXA XT, ALEXA XT Plus and ALEXA XT Studio cameras shipped between January 1, 2015 and the first shipment of ALEXA SXT cameras, we offer a full SXT Upgrade for free, which is called SXT Upgrade 15/16. This offer is good for one year after first shipment of ALEXA SXT cameras. The upgrade has to be done by ARRI Service in Munich, London, Los Angeles, New York, Beijing, Hong Kong or Mumbai. This offer is not available for ALEXA XT M cameras, ALEXA Classic cameras or ALEXA Classic cameras with the XR Module upgrade. 

All customers who bought an ALEXA XT, ALEXA XT Plus or ALEXA XT Studio before January 1, 2015 can purchase the SXT Upgrade 13/14 to upgrade from an XT to an SXT camera. 



Why do you not offer the SXT upgrade for free for XT cameras shipped before January 2015?

First off, those who had bought a camera a while ago have already had the ability to make some money with the camera. And second, we also have to make some money to finance all that development, so we can't extend an offer like that forever into the past. There has got to be a cut-off point that makes financial sense for our customers and for us. 

Why is there no ALEXA SXT M upgrade and no ALEXA SXT M?

The ALEXA Mini takes the place of an ALEXA SXT M, plus is a lot smaller. 

What happens with the DNxHD license of my XT camera when it is upgraded to an SXT?

ALEXA SXT cameras do not have the option of recording DNxHD. If an XT camera to be upgraded to an SXT has a DNxHD license, the upgraded camera will not have the license anymore. 

2. ALEXA SXT Features
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Is there a short overview of the new features of the ALEXA SXT?

You can download a short overview right here. The version with the dark background is designed for high quality printing and the version with the light background works well on any printer. If possible, print on front and back of one piece of paper so it is easy to carry around. 

ALEXA SXT Crib Sheet (display version)
ALEXA SXT Crib Sheet (print version)
ALEXA SXT Crib Sheet (display version, US Letter format)
ALEXA SXT Crib Sheet (print version, US Letter format)

What are the main features of the ALEXA SXT Cameras?

Here is the short list:

  • New Recording Formats
  • New ARRI Look Management
  • Super flexible on-set monitoring
  • Improved image quality
  • Single speed mode
  • New media bay and drives
Can you give a more detailed list?

And here is a slightly longer list with more details:

  • New recording formats
    • 16:9 ProRes 4K UHD (3840 x 2160)
    • The easiest and fastest path to the best 4K UHD  image, with the immediacy and speed of ProRes. Exactly the same format as on ALEXA Mini and AMIRA. 
    • Open Gate ProRes 4K Cine (4096 x 2636)
    • Unique to ALEXA SXT. Recorded file contains 4K cine standard width with extra height for VFX tracking markers or repositioning. 
    • 6:5 ProRes 2K Anamorphic (2048 x 858)
    • The most economical path to the best overall image quality with anamorphic lenses. Camera creates a ready-to-view ProRes file in the 2K DCI delivery format, with no de-bayering, cropping, rescaling or de-squeezing needed in post. 
    • 6:5 ProRes 4K Cine Anamorphic (4096 x 1716)
    • The most economical path to the best overall image quality with anamorphic lenses. Camera creates a ready-to-view ProRes file in the 4K DCI delivery format, with no de-bayering, cropping, rescaling or de-squeezing needed in post. 
    • 4:3 ProRes 2.8K (2880 x 2160)
    • This format provides extra height for VFX tracking markers or repositioning when shooting 16:9 or 1.85 projects. Lower data rate and smaller image circle than Open Gate. Same pixel count as 4:3 ARRIRAW 2.8K. 
    • Open Gate ProRes 3.4K (3424 x 2202)
    • Maximum image area
and photo site count
from a Super 35 ALEXA
in combination with the immediacy and speed of ProRes. Same pixel count as ARRIRAW Open Gate 3.4K. 
    • 16:9 ARRIRAW 3.2K (3168 x 1782)
    • The largest number of pixels that can be processed at 120 fps. About half the data of ARRIRAW Open Gate 3.4K. Use full 3.2K image area for most ARRI Super 35 PL lenses, or use 2.8K center for lenses with a smaller image circle (and gain padding). 
  • New ARRI Look Management
    • Look management from prep to post
    • Maintain and share the cinematographer's intended look on set, in dailies and in editing
    • Wide range of unique looks possible
    • Same look file and tools for ALEXA SXT, ALEXA Mini (SUP 4.0) and AMIRA (SUP 4.0)
    • ARRI Look File is always stored in metadata for 
      • Live grading on set
      • Automated dailies creation
      • Editing with looks 
  • Super flexible on-set monitoring
    • High Dynamic Range (HDR) monitoring
    • Rec 709 or Rec 2020 monitoring outputs
    • Four independent monitoring outputs
    • Better frame grabs
  • Improved image quality
    • Optional ARRI Noise Reduction (ANR)
    • Advanced defect pixel correction
    • More range for baked-in looks with 3D LUTs
  • Single speed mode
    • Switch instantly to any frame rate without a switch from regular to high speed mode
  • Powerful new media bay and new drives
    • Supports new high speed SXR Capture Drives (1 TB and 2 TB) via SXR Adapter
    • Supports current XR Capture Drive 512 GB via XR Adapter
    • Supports SxS PRO and SxS PRO+ cards via SxS Adapter 2
    • Supports CFast 2.0 cards via CFast 2.0 Adapter 2
    • Increased frame rates for some recording formats
    • ProRes RAID; redundant recording to XR and SXR Capture Drives
How can I learn more about the ARRI Look Management?

If you want to learn more about the ARRI Look Management please download our ARRI Look Management White Paper

Which third party products support the ARRI Look Management?

Live grading on set with the ARRI Look Management is supported by Pomfort LiveGrade, Codex Live, Colorfront On-Set Live, Filmlight Prelight, Technicolor DP Lights and others. 

Automated dailies creation with the ARRI Look Management is supported by DaVinci Resolve, Colorfront OSD, Codex Production Suite, Pomfort Silberstack, Filmlight Daylight and others. 

Editing with looks through the ARRI Look Management is supported by Avid Media Composer, Apple Final Cut Pro X and Adobe Premiere.

In all cases, check with the manufacturer to make sure you have the software version that supports the ARRI Look Management.  

What features are not available in ALEXA SXT cameras?

Some features of previous ALEXA cameras are not available in ALEXA SXT cameras anymore:

  • ALEXA SXT cameras do not have the option of recording DNxHD, since DNxHD was simply not very popular as a recording format. 
  • ALEXA SXT cameras do not support the Fiber Remote option. 
  • ALEXA SXT cameras do not support 8, 16 and 32 GB SxS PRO cards. 
  • ALEXA SXT cameras do not support ALEXA Look Files with a 1D LUT. Instead, they use the new ARRI Look File 2 with ASC CDL and 3D LUT support. 
  • ALEXA SXT cameras do not support the SUP 10/11 CDL server functionality. This functionality has been replaced by the new AFL-2 (CDL & 3D LUT) metadata capture. 
3. ALEXA SXT Media
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What Media can I use with ALEXA SXT cameras?

ALEXA SXT camera support the following media. Each media needs one of four new adapters. The adapters from the ALEXA XT will not work in ALEXA SXT cameras. 


 

Why can I not use the existing adapter from the ALEXA XT cameras?

As we like to have everything backwards compatible, using the existing adapters was our first design intention. However, since the SXR Capture Drives needed a new high speed connector, you can end up with more electrical interfaces than is good for signal integrity. So we chose one adapter for each media family, which combines the greatest flexibility with the best signal integrity.

Why does ALEXA SXT not support SanDisk CFast 2.0 cards?

ALEXA SXT will support the new LEXAR 256 GB cards, as there has been very little use of the SanDisk 128 GB cards by ALEXA XT owners so far. We assume that customers who buy a new ALEXA SXT will also buy new media.

Why can I not use all media that is supported in former ALEXA cameras also in ALEXA SXT cameras?

To reduce testing time and due to low demand in using this recording media, we decided that ALEXA SXT does not support SxS PRO 8, 16 and 32 GB cards, all SanDisk CFast 2.0 cards and LEXAR CFast 2.0 128 GB cards.

What software do I need to read SXR and XR Captures Drives that were used in ALEXA SXT cameras?

Please note that when recording XR Capture Drives or SXR Capture Drives in the ALEXA SXT, one must always use the Codex Production Suite 4.1 software. The older Codex dts 3.x software may not be used anymore; while it seems to work with XR Capture Drives recorded in an ALEXA SXT, it creates a number of significant problems as it does not understand the metadata properly. The ARRIRAW Converter and SDK 5.3 are not affected and do not cause a problem.

Customers who purchase a new XR or SXR Thunderbolt Capture Drive Dock will receive the Codex Production Suite 4.1 for free. Owners of older Capture Drives docks can sign up on the Codex website (codex.online) for a version of the Production Suite 4.1 that includes a 30 day trial of the full Production Suite. After 30 days the customer can purchase a 12-month Codex Connect subscription, which includes the full Production Suite. Even without the Codex Connect subscription, the software will retain the basic functionality of downloading ProRes and ARRIRAW files.

In order to download ProRes from XR and SXR Capture Drives that have been formatted and recorded in an ALEXA SXT, the ARRI RAID driver has to be installed on the Mac that the dock is connected to. The ARRI RAID driver is provided as part of the Codex Production Suite 4.1 software and is necessary to read ProRes from XR and SXR Capture Drives with the ALEXA SXT. Make sure to select the “Capture Drive RAID support” option while installing the software.

ALEXA Mini records ARRIRAW on CFast 2.0 cards. Why do I need SXR or XR Capture Drives to record ARRIRAW with ALEXA SXT cameras?

At this point in time we are evaluating the option to allow the ALEXA SXT recording MXF/ARRIRAW to CFast 2.0 cards as well. 

Do I need to buy all new SXR Capture Drives when I get an XT upgraded to SXT?

No, the existing XR Capture Dries will work well with the ALEXA SXT cameras. SXR Adapter and XR Adapter are included in SXT upgrades (and in new camera sets as well). SXR Capture Drives have a higher capacity and offer higher frame rates in some recording formats. The table ‘Maximum Frame Rates – Overview’ will give you an overview of the advantages in recording with SXR Capture Drives. 

Can I use SxS PRO+ 256 GB cards (SBP-256D) with ALEXA SXT?

Currently no. Support for SxS PRO+ cards (SBP-256D) is planned for a future SXT Software Update Package.

What are the different methods of clearing data of Recording Media?

There are two methods for clearing old data from a recording medium with ALEXA SXT cameras: Quick Format and Erase. For technical reasons, most media allows only one of those methods. Quick Format erases only the file allocation table, but leaves the actual data still on the card. Quick Format is therefore the faster method. Erase takes longer than Quick Format, but ensures that all data on the card is erased. Using Erase with SxS PRO/PRO+ cards can increase their write speed.

4. ProRes RAID
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What does RAID mean?

RAID (redundant array of independent disks) is a data storage technology that combines multiple physical disk drives into a single logical unit for the purposes of data redundancy, performance improvement, or both. Of the many RAID types available, we use RAID 0, RAID 1 and RAID 10 in ALEXA SXT.

RAID 0 consists of striping, where multiple single disks are combined into a single volume. The capacity of a RAID 0 volume is the sum of the capacities of the disks in the set.

RAID 1 consists of data mirroring, where data is written identically to two (or more) drives, thereby producing a "mirrored set" of drives.  

RAID 10 is a nested (hybrid) RAID type, where two disks create a mirrored RAID 1 volume, and then two of those volumes are combined into one logical RAID 0 volume. In most cases RAID 10 provides better throughput and latency than all other RAID levels except RAID 0.

 

Can I turn the ProRes redundancy function off?

No, in ALEXA SXT cameras, both XR and SXR Capture Drives always use RAID redundancy when recording ProRes.

Is this redundancy also available for ARRIRAW recording?

No, at this point in time Capture Drives have proven to be very reliable, so we do not think this is necessary.

So why did you provide RAID for ProRes, then?

For technical reasons, ARRIRAW can use the full capacity of the Capture Drive, while ProRes can only use half of the drive's capacity. Rather than let half the drive go to waste when recording ProRes, we thought we might use this free capacity to add some data safety, even though Capture Drives are already one of the safest media available. This also makes sense as ProRes has a lower data rate than ARRIRAW, and so much more ProRes can be recorded onto a single drive than ARRIRAW, especially now that 1 TB and 2 TB Capture Drives are available.

Is this redundancy also available for SxS PRO, SxS PRO+ and CFast 2.0 cards?

No, the RAID redundancy is only available for XR and SXR Capture Drives in the ALEXA SXT.

Is there an ARRI RAID driver for windows?

No. Since the SXR Capture Drive dock only works in conjunction with Codex software and there is no Codex software for Windows, a Windows ARRI RAID driver would make no sense.

5. Sensor Modes, Recording Formats, Distribution Formats
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Can you explain the differences between sensor modes, recording formats and distribution formats?

A sensor mode defines an aspect ratio, which defines the area on the sensor that is being captured. A recording format define what is being recorded in-camera in the file. So while a sensor mode defines a certain number of photosites on the sensor, those may be recorded straight or up or down-sampled to create the pixels of the recording format. A distribution format defines how the final product is delivered to the consumer. The contents in the recording format is often up or down-sampled, cropped, repositioned or rotated in post before it becomes the final distribution format.

An example: Choosing a 16:9 sensor mode on the ALEXA SXT allows the further choice of various recording formats. Choosing the 4K UHD recording format means that a 16:9 area from the sensor is read out, up-sampled in camera to a 4K UHD image and then recorded. In this case the recording format of 4K UHD is the same as the distribution format of 4K UHD. 

What sensor modes are supported by ALEXA SXT cameras?

ALEXA SXT camera support four sensor modes, 16:9, 6:5, 4:3 and Open Gate. Below is a basic guide to those sensor modes and the most often used recording formats. 



The 16:9 sensor mode is most often used for TV shows that need an HD or a 4K UHD deliverable. For the 16:9 HD recording format, 2.8K from the sensor are used. For the 16:9 4K UHD recording format, 3.2K from the sensor are used. The 16:9 2.8K sensor mode can also be used to derive a 16:9 2K Cine recording format. 



The 6:5 sensor mode (formerly called "4:3 Cropped" in the ALEXA XT) is used exclusively for any shooting with anamorphic lenses. Since anamorphic lenses squeeze the 2.39:1 image by a factor of 2, the resulting area used on the sensor has a 1.195:1 aspect ratio, which is 6:5. 



The 4:3 sensor mode is as tall but slight wider than 6:5. Shooting 4:3 has become popular for VFX heavy feature films in the 1.85:1 aspect ratio (dotted line). The area above and below the 1.85:1 image is used for placing VFX markers and/or for up/down repositioning. 



Open Gate uses the full sensor area of the ALEXA camera. This format has become popular for those shooting feature films in 2.39:1 or 1.85:1. The extra area above and below the image is used for placing VFX markers or for up/down repositioning. The extra resolution provides the best result when up-sampling to a 4K Cine recording format. 

6:5? What the hell? I thought you needed 4:3 for anamorphic?

The 4:3 aspect ratio was originally left over from the film days, and now has been put to good use by VFX-heavy feature films. Anamorphic lenses don't actually need the full width of the 4:3 image; they squeeze the 2.39:1 image by a factor of 2, and the resulting area used on the sensor has a 1.195:1 aspect ratio, which is roughly 1.2:1, which is 6:5. When shooting with anamorphic lenses in 4:3 sensor mode, you always have to crop the extra area to the left and right of the image in post, an extra processing step that is avoided by shooting in 6:5. 

In the ALEXA XT cameras with SUP 11 we have introduced this mode, however, there it was still called '4:3 Cropped', but that is the same thing as the ALEXA SXT 6:5 sensor mode. 

How can I know which lenses will work in Open Gate sensor mode?

Look in the TOOLS section of the ALEXA web pages at the ARRI Lens Illumination Guide

Every lens is brighter in the center than in the corners: that is called the lens illumination. To get a feeling for how lenses perform in Open Gate, you first choose a sensor mode and what framelines you want to check out. Then you choose a lens model, focal length, iris and focus setting, which are all parameters that affect lens illumination. The resulting image will show how the illumination falls off towards the corners and if you get vignetting. We have most ARRI lenses in there already, but the guys are still shooting, so we will add more lenses as time goes by. You can see the result right there on the screen or save the images as a JPEG file. 

Some lenses do better and others worse. One of the lenses that does really well is our Ultra Wide Zoom UWZ 9.5 - 18; it was designed for a large image circle. Most primes under 18 mm have an issue shooting Open Gate, so the UWZ really solves the question of how to shoot wide angle with Open Gate.

Click image to enlarge

What recording formats are supported by ALEXA SXT cameras?

ALEXA SXT cameras can record ARRIRAW just like the XT cameras could, but now with higher frame rates:

16:9 ARRIRAW up to 120 fps, 6:5 ARRIRAW up to 96 fps, 4:3 ARRIRAW up to 96 fps and Open Gate ARRIRAW up to 90 fps. 

ALEXA SXT cameras can record ProRes in HD, 2K Cine, 3.2K, 4K UHD or 4K Cine and also in the anamorphic sensor mode 6:5 in 2K and 4K. And they can do that with all high-end ProRes flavors from ProRes 422 to ProRes 4444 XQ.

What are the two recording formats ‘6:5 ProRes 2K Anamorphic’ and ‘6:5 ProRes 4K Anamorphic’ doing with my images?

These two new recording formats allow shooting an anamorphic format with the fast and proven ProRes workflow. 

6:5 ProRes 2K Anamorphic' is the most economical path to best overall image quality with anamorphic lenses for a 2K deliverable. In addition to the immediacy and speed of the ProRes workflow, 6:5 sensor mode captures only the sensor area needed for anamorphic lenses, thus avoiding cropping steps in post and providing an increase in frame rate versus 4:3 sensor mode. Additionally, the camera already debayers, down-samples and de-squeezes the anamorphic image to record a ready to view image in the 2K DCI delivery format (2048 x 858). 


6:5 ProRes 4K Cine Anamorphic' is the most economical path to best overall image quality with anamorphic lenses for a 4K deliverable. In addition to the immediacy and speed of the ProRes workflow, 6:5 sensor mode captures only the sensor area needed for anamorphic lenses, thus avoiding cropping steps in post and providing an increase in frame rate versus 4:3 sensor mode. Additionally, the camera already debayers, up/down-samples and de-squeezes the anamorphic image to record a ready to view image in the 4K DCI delivery format (4096 x 1716). 

Why would I want to shoot ProRes 3.2K?

ProRes 3.2K is a recording format that is quickly gaining popularity. It is being used on major TV series like Game of Thrones, on many Amazon projects and on various feature films. The reason is that it has a lower data rate than ProRes 4K UHD (in fact about 33% less data) and thus is less expensive to record on set and to process in post. It can then be used for an HD or 2K deliverable (with extra image area for re-sizing, rotating, re-framing or stabilizing) or, with only a slight up-sample, for a 4K UHD deliverable. 

Why are there so many recording formats?

With the 14 different recording formats we have in the ALEXA SXT we are offering the best image quality and most efficient workflow for the most common production, post and distribution requirements. The recording formats are optimized for different budget situations, market segments, distribution resolutions and aspect ratios, lens choices and necessary post steps including the amount of VFX work.

How can I find out how many photosites and pixels are used for my recording format?

The PDF Document “ARRI Recording Resolutions Overview” will give you an insight of used photosites and pixels of ALEXA and AMIRA cameras. You can also look at the "ALEXA SXT Crib-Sheet” that summarizes all new features of the ALEXA SXT and also includes the information about used photosites and pixels. 

In addition, the ARRI Frameline Composer will also output the used photosites on the sensor (“Sensor”) and pixels of your recording format (“Recording”).

Click image to enlarge.

Why are the actual pixel counts sometimes different between ARRI cameras?

We are always striving to provide the best performance for each platform. As a result, there sometimes are minor differences in the actual pixel count of our recording formats. However, we are aiming to standardize as much as possible with the new cameras.

One example for this is the Open Gate format differences between ALEXA XT, ALEXA SXT and ALEXA Mini. When we first created the Open Gate format for the ALEXA XT in 2012, we had to record the full 3424 x 2202 because there are certain hardware based rules on how many pixels we can push through the camera and record. However, we found that some pixels on the edge of the frame could not be corrected by the dynamic defect pixel correction (DDPC), and so we decreed that you shall only use 3414 x 2198 of those 3424 x 2202. This 3414 x 2198 active image area is noted in metadata and the post production software should only process this area. Otherwise the very edges of the image may contain image artefacts.

While working on the ALEXA Mini and then subsequently on the ALEXA SXT, our engineers have worked out a way to make the DDPC function all the way to the edge, so now we can record and give you the full 3424 x 2202, which is, admittedly, much easier for all involved. We are planning to also provide this in the next Software Update Package (SUP 12.0) for ALEXA XT cameras.

We know that this is sometimes confusing, especially if you are preparing a shoot with different ARRI cameras. To get an overview of similarities and differences of the pixel counts of ARRI cameras please take a look at the ARRI Recording Resolutions Overview.

6. ProRes 4K
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How can you record ProRes 4K in-camera when the sensor has 3.4K photosites?

ALEXA SXT cameras use the extra horse power of the ALEXA 65 electronics to perform a mild up-sample in-camera, either to ProRes 4K UHD or to ProRes 4K Cine. The number of photosites are only one of many parameters that form a quality 4K image. The combination of ALEXA's best image overall image quality with the new processing chain and the relatively small up-sample factor of 1.2x preserves the fundamental qualities of the ALEXA picture that filmmakers so love.  

I thought you had to over-sample to get a good image. Why is up-sampling now OK?

The short answer is that our understanding of what is important to create a good looking image has changed, technology has advanced and the ALEXA overall image quality is so good that it up-samples beautifully. 

Here is the long answer: Scientifically, if you want the best resolution of a black and white test chart, you should over-sample, i.e. have more photosites on the sensor than pixels in your recording format. However, an image is not just resolution and, if I may quote Rodney Charters here, movie making is not a science project. Some people talk as if all a cinematographer does all day is shoot black and white test charts, and resolution is the most important image quality parameter. But that is not the case. Real world images are vastly different from black and white test charts, and the overall image quality is defined by many more parameters. It is crazy to look at just one aspect, i.e. resolution, and make all decisions based on that. Parameters like the absence of artifacts, dynamic range, color rendition, color gamut, noise level, temporal resolution and the quality of the debayer are actually much more important for overall image quality than just resolution. 

And the technology has changed. Debayering has gotten much, much better, the electronics are much more powerful and we have learned a lot about in-camera image processing and up-sample algorithms. We have a whole color science department that continually pushes the envelope of what is possible. They came up with our in-camera up-sample algorithm which is just fantastic. 

So at some point we entertained the idea to do this mild up-sample from 3.2K photosites on the sensor to 3.8K (=  4K UHD) pixels in the file. And there were some inside ARRI who were opposed to that. But we have learned that the theory will only get you so far and at some point the only way to really know is to shoot a test. And the results looked great. In fact, we compared it to some 'native' 4K images and our up-sampled images looked as good, if not better. That convinced everybody within ARRI that it's possible to do a mild up-sample of 1.2x and still get the beautiful images everyone is used to from ALEXA. Now we have an answer for those who need to record a 4K image, be that in 4K UHD or 4K Cine.

What is the difference between ProRes 4K UHD and ProRes 4K Cine?

The ProRes 4K UHD recording format (3840 x 2160, 16:9) is designed for a 4K UHD TV distribution format (3840 x 2160, 16:9). ProRes 4K UHD is derived from 3200 x 1800 photosites on the sensor in 16:9 sensor mode. These are the same values as used in AMIRA and ALEXA Mini. 

The ProRes 4K Cine recording format (4096 x 2636, 1.55:1) is designed for the 4K DCI cinema distribution format container (4096 x 2160, 1.9:1). ProRes 4K Cine is derived from 3414 x 2198 photosites on the sensor in Open Gate sensor mode. We are not taking the full Open Gate of 3424 x 2202 to up-sample to ProRes 4K Cine since the slightly smaller size of 3414 x 2198 gives us better results in up-sampling. ProRes 4K Cine is unique to the ALEXA SXT cameras in ARRI's line of cameras.

Both formats use the same high quality 1.2x up-sample filter. 

Why does the ProRes 4K Cine recording format have more lines than the 4K DCI distribution format?

The 4K Cine recording format contains 4096 x 2636 pixels, which is 476 lines more than the 4K DCI distribution container (4096 x 2160). This extra area above and below the image is designed for up/down image repositioning or placing of VFX markers. This is an example where the recording format purposefully contains more than is needed in the distribution format to provide for some added flexibility in post.

7. Current and Future ALEXA Sensors
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Isn’t the ALEXA sensor getting past its prime in terms of Moore's Law?

First, we don't think that Moore's Law is applicable to sensor design.
Second, the photosite design of the ALEV 3 sensor is unique. That design provides the great dynamic range and the highlight handling that the ALEXA has, it provides the sensitivity, the low-noise floor and the beautiful skin tones. This sensor design combined with the ever improving processing chain has stood the test of time. So far we have not seen any camera that comes close, so we think we have a really unique piece of technology here. 

Are you working on a new sensor?

Of course we are working on a new sensor, we are a camera manufacturer. However, we're only going to release it in a product if we can achieve better overall image quality as ALEXA. And the image quality of the ALEXA is really hard to beat, even for us. The ALEXA SXT is a fantastic piece of gear with many new options tailored for today's professional productions. 

Should I invest in an ARRI camera when 4K will be standard in the future?

Yes. All the latest ARRI cameras (AMIRA, ALEXA Mini, ALEXA SXT) are capable of 4K recording. Since all ARRI digital cameras produce best overall image quality and have the highest dynamic range of any digital production camera, the also produce the best looking 4K images.

If all ARRI cameras use the same sensor, why are ALEXA Minis and AMIRAs running 200 fps and ALEXA SXT 120 fps?

ALEXA Minis and AMIRAs are using a later revision of the ALEV 3 sensor, which is the same as the revision used in ALEXA SXT, except that it runs at a higher clock rate. This provides the higher maximum frame rates. It was not possible to integrate this revision into the ALEXA SXT for hardware compatibility reasons. 

8. ALEXA SXT High Dynamic Range
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ALEXA SXT High Dynamic Range

For more information about HDR capturing, monitoring and post production with ARRI cameras please visit our High Dynamic Range FAQ 

9. Miscellaneous
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The side display of the ALEXA SXT camera seems to be darker than the side display of the XT camera. Why is that?

We needed to change the type of side display since the manufacturer of the original side display phased out the product. During the upgrade from XT camera body to SXT camera body the display will not get changed. All new build SXT cameras will get the new side display.