Lens Data System FAQ
Common questions regarding ARRI's Lens Data System
Common questions regarding ARRI's Lens Data System
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.
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.
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 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.
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.
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).
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):
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: