Lens Data System FAQ

The Lens Data System (LDS) provides various time and money saving features by displaying lens data and camera related information on our WCU hand unit, in status overlays in-camera or on connected monitors/video assist for easy communication. In addition it brings additional benefits in post-production: all the lens data is being carried through the pipeline and embedded in the original camera negative files for use in VFX.

Advantages

Lens data display on the WCU‑4 hand unit including lens scales and dynamically displayed depth of field. That allows the assistant to quickly judge whether the object is still within the depth of field.
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 (also: no focus rings have to be made during prep).
Focus tracking synchronizes the output of the UDM distance measuring device with the focus motor. Good for zoom-racks on the clapper board.
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-production.

In Summary the LDS reduces the assistants work load and makes working with cameras and lenses more efficient. The advantages of the LDS where first introduced with the ARRICAM System and then expanded to the 435 Advanced. With the introduction of our digital camera systems, especially the ALEXA camera, the data made its way into post production, where the data eliminates complex calculations and meticulous measuring – which spares the budget.

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
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:

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)

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.

If the 1^st 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.

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

Ask the 1^st 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.

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.

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

Compatible post tools support the “ARRI Metadata Bridge” 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.

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.

flow graph showing how metadata is distributed throughout the LDS environment

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.

EF-Lenses are supported on ALEXA Mini and AMIRA with SUP 5.0 or higher. Apparently their data is not precise enough for our Electronic Control System (ECS) environment.

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.

LDS-2 is the next evolution of ARRI’s Lens Data System for our Electronic Control System and a new generation of lenses. LDS-2 delivers more accurate and faster lens data.

Compared to LDS-1 it eliminates the need for initial calibration through absolute encoders which cuts time on set when changing lenses. The new system uses a 8.7x faster interface that enables lens manufacturers to send more data to the camera than before.
LDS-2 extends the possibilities of lens data and is being licensed to other lens and camera manufacturers.

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 has 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.

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.

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).

LDS-2 support:

ALEXA 35
ALEXA Mini LF
ALEXA LF

LDS-1 support:

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

Original camera negatives from ARRI cameras (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

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

LDS-2 lenses:

ARRI Signature Primes

LDS-1 lenses:

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

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

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.

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.