Lens Data System FAQ

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What is LDS?

The ARRI Lens Data System (LDS) is part of the Electronic Control System (ECS), formerly known as LCS (Lens Control System), WLCS (Wireless LCS), and WRS (Wireless Remote System). LDS was been introduced in 2000 with the LDS Ultra Prime and Master Prime lens series, then used in combination with our film cameras. As a solid companion for visual effects work, it was incorporated into our digital camera systems including the popular ALEXA series of cameras.

 

LDS describes digital lens settings. Lenses with LDS functionality deliver information about its current settings (focus, iris, zoom) to the camera; the camera interprets these values and transmits the information to its recording module and optionally to any further accessories connected to the LCS such as a Wireless Compact Unit WCU-4 or Master Grips.

Why should I use the LDS system?

Using LDS creates an immediate benefit on set: it eases communication by displaying information like t-stop, focal length, and focus distance on the monitoring output. The data can be used for focus mapping and focus tracking with ARRI’s WCU-4 or as a readout display on the wireless hand unit or on a monitor.

A big advantage for ACs bears within the “pre-marked focus rings”: pre-marked rings are a big time saver in prep, they also uncouple focus scales of a lens from the focus ring of the handset. This allows you to choose the best scale for your shooting situation.

Frame accurate lens data captured with the images eliminates guesswork in VFX. By incorporating the ARRI Metadata Bridge, third-party tools can automatically transport metadata from ARRIRAW files to Open EXR and DPX files – a time and money saver for postproduction. High quality of captured lens data is ensured if the same data has already been used on set by the camera assistant for lens data display, focus mapping or focus tracking.

 

The benefits in brief:

 

  • Lens data display on the WCU-4 hand unit (including lens scales and depth of field), the Master Grips, the camera monitoring outputs, the electronic viewfinder, and the camera menu display for easy communication.
  • Focus mapping to pre-marked rings uncouples focus scales of a lens from the focus ring of the handset and allows you to choose the best scale for your shooting situation.
  • Focus tracking synchronizes the output of a distance measuring device with the focus motor.
  • Lens data for postproduction eliminate guesswork in VFX. Through the ARRI Metadata Bridge third-party tools can transport metadata from ARRIRAW files to OpenEXR and DPX files – a time and money saver for post.
What’s the advantage of an LDS lens over a regular lens?

Lenses equipped with LDS have data encoders installed on all geared rings that constantly report their positions to the camera. The camera not only knows the lens type and serial number, but also dynamic information like focal length (variable for zoom lenses) focus distance (in imperial or metric units), and current aperture. Moreover, this reporting takes place via robust internal connectors at the lens mount, adding no weight or complexity to the camera package. Lenses without LDS do not by themselves offer any kind of information to the system – they need to be adapted via the Lens Data Archive (LDA).

Which cameras support LDS?
  • ARRI ALEXA and ALEXA XT cameras with “PLUS module” and/or PL-LDS Mount
  • ALEXA SXT cameras

  • ALEXA 65
  • ALEXA Mini
  • AMIRA equipped with PL LDS lens mount
Which lenses have built in LDS?
  • ARRI/Zeiss Master Primes
  • ARRI/Zeiss Master Macro 100
  • ARRI/Zeiss Master Anamorphics
  • ARRI/Zeiss LDS Ultra Primes
  • ARRI/Zeiss Master Zoom 16.5 - 110
  • ARRI/FUJINON Alura Lightweight Zooms
  • ARRI/FUJINON Alura LDS Extender
  • ARRI Ultra Wide Zoom 9.5-18
  • ARRI Anamorphic Ultra Wide Zoom 19-36
How can I use non-LDS lenses with the ECS system? What does a LDA do?

Lenses without LDS can be integrated into the system via the Lens Data Archive (LDA). By mapping a lens all information about the lens, its scales, name, and serial number can be transferred into a lens archive. When using the lens the next time all that has to be done is to load the lens file for that lens from the Lens Data Archive and calibrate the motors.

 

It takes about 5 minutes to map a lens: after attaching the lens and connecting and calibrating motors (or Lens Data Encoders) on each axis of the lens, the mapping can be done with the Wireless Compact Unit (WCU-4) or the web remote of the ALEXA camera.

 

These lens files can be loaded to any camera employing the Lens Data Archive or the Universal Motor Controller UMC-4.

Which lenses are part of the Lens Data Archive?
  • ARRI/Zeiss Master Primes
  • ARRI/Zeiss Master Macro 100
  • ARRI/Zeiss Master Anamorphics
  • ARRI/Zeiss Ultra Primes
  • ARRI/Zeiss LDS Ultra Primes
  • ARRI/Zeiss Ultra 16 Primes
  • ARRI/FUJINON Alura Zooms
  • ARRI Ultra Wide Zoom 9.5-18
  • Zeiss Compact Primes
  • Zeiss High Speed Primes
Why are LDS lenses part of the LDA?

ARRI’s LDS lenses can be used on all PL-mount equipped cameras. To be able to assist you with ARRI LDS if no ARRI camera is around, the UMC-4 needs to have as many lenses in its archive as possible – even the LDS lenses. That may seem paradoxical, but

having the LDS lenses in the archive is like a fail-safe: in case a lens or lens mount has a defect, you can still get valid lens data while using it, with the help of the lens table from the Lens Data Archive.

How is the LDS organized? Is there a main unit?

The LDS is powered by the camera device in its center – the ALEXA, ALEXA Mini, or AMIRA camera or the Universal Motor Controller UMC-4 – that broadcasts all values through the whole system to assure 100% consistency throughout all connected devices.


What is needed to create actual lens data?

Lens data is generated through the combination of encoder values with a “translation table,” the lens file (*.tab).

A LDS lens comes equipped with internal encoders – also the lens file is built in. As soon as the lens connects to a LDS lens mount, the lens file travels to the LDS core; once initialized, a constant stream of raw encoder values follow. The core unit, in this case the camera, computes human readable values using the “translation table.” Both sets of values – the raw encoder values and the human-readable ones – are saved within the corresponding metadata fields and forwarded to other ECS accessories.

From a VFX point of view: What needs to be done to transport the LDS information to post?

If the 1st AC is using ECS equipment to pull focus and the camera originals are delivered straight to VFX, the metadata will be directly available for VFX as it is embedded in the camera originals. See the next question to find out how to access that metadata.

 

If the 1st AC is not using ECS equipment to pull focus, then:

 

Ask the 1st AC to:

 

  • initialize the lenses by turning the lens rings (in case of LDS lenses)
  • load the right lens table from the Lens Data Archive (with every lens change)

 

 

For some productions, VFX will get the original footage before any conversion. This is the best guarantee that all metadata (LDS metadata and otherwise) will be available to assist VFX work.

 

If the output of the camera is not being delivered directly to VFX (this is most likely because the file format required by VFX is different than the file format used to capture content; in an ideal world, all the original camera output metadata would be passed through in the OpenEXR or DPX files provided to VFX), an ARRI-provided tool, ARRI Meta Extract, can be used to extract the metadata from both the original frames and the frames provided to VFX.

 

This is an excellent test to make part of VFX pre-production, and can help you refine the conversion pipeline (to OpenEXR or DPX) so as to retain all the LDS and other possible metadata.


Can I access the information provided by the LDS? How do I give that information to post?

Sure, we strongly encourage you to do so.

 

  • All necessary information to access the metadata embedded in the SDI stream can be found in our “Metadata White Paper”: http://www.arri.com/?eID=registration&file_uid=17128
  • To access the metadata embedded in ARRIRAW or ProRes clips, download our free software “ARRI Meta Extract (AME),” in either its GUI or command-line tool form. In AME you can choose which part of the metadata you want to export and hand only that information over to another department: http://www.arri.com/camera/alexa/tools/arri_meta_extract/.

    The output of ARRI Meta Extract is a *.csv file, the same file our UMC-4 provides on SD cards, using the same attribute names with the same type of attribute values. That means even if you are shooting with a third-party camera, LDS metadata can find its way to you. You don’t have to alter your metadata pipeline.

    Also our viewer for ARRIRAW, the ARRIRAW Converter, displays lens metadata in the metadata viewer (Tab: Look, Color, Lens & VFX)
How do I make sure my lens metadata end up with VFX (Open EXR, DPX files)?

Here is a list of compatible post tools that support the “ARRI Metadata Bridge” (tools that hand over all header information/metadata from ARRRIAW source files).

We have confirmation from Colorfront (2016 Update 2 of Transkoder and OSD), Filmlight (Baselight (version 4.4m1), and Daylight (version 4.4m1.8973)) to be “metadata-aware.”

Which metadata is contained within the LDS?

The LDS transports a set of different data types. Some of them are human readable some are raw encoder values (or information for other hardware):

 

  • Lens Model
  • Lens Serial Number
  • Lens Distance Unit
  • Lens Focus Distance
  • Lens Focal Length
  • Lens Iris
  • RawEncoderFocus RawLds
  • RawEncoderFocus RawMotor
  • RawEncoderFocal RawLds
  • RawEncoderFocal RawMotor
  • RawEncoderIris RawLds
  • RawEncoderIris RawMotor
  • EncoderLimFocusLdsMin
  • EncoderLimFocusLdsMax
  • EncoderLimFocusMotorMin
  • EncoderLimFocusMotorMax
  • EncoderLimFocalLdsMin
  • EncoderLimFocalLdsMax
  • EncoderLimFocalMotorMin
  • EncoderLimFocalMotorMax
  • EncoderLimIrisLdsMin
  • EncoderLimIrisLdsMax
  • EncoderLimIrisMotorMin
  • EncoderLimIrisMotorMax
  • Lds Lag Type
  • Lds Lag Value (lag in ALEXA cameras is one frame)
  • Lens Linear Iris
  • ND Filter Type
  • ND Filter Density
  • Camera Tilt
  • Camera Roll
  • Master Slave Setup Info
  • 3D Eye Info
Which file types support the transport of LDS metadata?
  • Original camera negatives (ProRes, ARRIRAW or MXF/ARRIRAW files)
  • Open EXR generated form ARRIRAW Converter or software solutions of our partners with built-in ARRI Metadata Bridge
  • DPX generated with ARRIRAW Converter or software solutions of our partners with built-in ARRI Metadata Bridge
How can you superimpose the lens data into ALEXA’s monitoring output?

In the menu go to MONITORING > MON OUT 1 > Framelines & Status info; scroll all the way down; set LDS info to “ON.”

Is there a read-out display for manual follow focus systems?

LDS information can be easily monitored on the MON-OUT information overlay or the LDS menu page. When you are working with LDS lenses and manual focus units, it is a plug and play setup. If you are working in a non-LDS environment on the other hand, a stand-alone encoder, LDE-1, is needed for every axis that needs to be tracked.

Does LDS work with third-party lens control units?

If the 1st AC is used to her/his third-party hand unit some steps need to be done to maintain LDS information for VFX use: either a LDS lens must be used or lens files need to be created for each lens. During production the LDE-1 encoder needs to be connect to the lens in order to gather the encoder values externally. Lens metadata will be fed to the camera device as if you were using a regular LDS setup.

 

Please note: Using a third-party focus system will not allow you to have the LDS information on the hand unit itself.

Cooke also offers lens data with its /i and /i2 technology. Is it compatible with LDS?

We offer compatibility with the Cooke /i protocol and ALEXA, ALEXA Mini, and AMIRA cameras. However, ARRI cameras currently do not retrieve information about the lens scales. Because of that we cannot get a graphical scale on the hand unit; it is also not possible to use focus tracking or focus mapping.

I’d like to work with EF-Lenses, are there any pitfalls?

EF-Lenses will be supported on ALEXA Mini with SUP 5.0, but their data is not precise enough for our Electronic Control System (ECS) environment.

How precise is LDS? Does it have a delay?

ARRI’s Lens Data System is a very high precision system. The LDS data comes with both a value and an offset field. From the camera, this offset will be, at maximum, one frame. In format conversions (e.g. from ARRIRAW to OpenEXR), some conversion applications may correct for this, producing derived files with a zero-frame offset.