The benefits of lens data

ARRI's Electronic Control System is a sophisticated toolset for precise wireless remote control of cameras and lenses from any manufacturer; it also provides valuable metadata about exactly what a lens is doing at any given moment. But just what is lens data and what is it good for?

Lens data is a continuous stream of information about the focus, iris and zoom settings of a lens, as well as the depth-of-field range. It can be displayed on the Wireless Compact Unit WCU-4, giving full remote control to the focus puller even if the camera is out of sight. With ALEXA Plus and Studio cameras, lens data is also viewable on the monitor outputs, viewfinder and side panel display, so the DP can see what the lens is doing from anywhere on set. Additionally, lens data is an important prerequisite for lens mapping and focus tracking.

Lens mapping is the mapping of a lens focus scale to a predefined, pre-marked focus ring. This saves time in prep, as the camera assistant does not have to mark up an individual ring for each lens. It also simplifies work on set, as the five pre-marked rings will cover multiple different lenses. With fewer rings, the focus puller will get familiar with them faster, allowing more intuitive focus pulling.

Focus tracking is a continuous, automatic focus adjustment based on the distance measured by an ultrasonic measuring device such as the UDM-1.

As well as offering on-set benefits, ARRI lens data reduces the time and effort required to achieve complex visual effects by helping to match a virtual lens to the recorded image in postproduction, or even driving the virtual lens optics in a real-time VFX system on set. Frame-accurate lens data is recorded in-camera by any ARRI digital camera equipped with a PL-LDS mount, or recorded by the Universal Motor Controller UMC-4 with any other camera, from any manufacturer.


Lens data generation has two basic requirements: first, the system needs to know where the lens ring is. This information comes from encoders, which are either built into the lens (LDS lenses), located inside lens motors or housed in a separate unit, like the Lens Data Encoder LDE-1. Second, the system needs to have a lens table that converts the raw encoder values into something a human can use, like T-stops and focus ring values. ARRI offers two basic configurations:

Option 1: LDS lens and LDS camera
Each LDS lens can detect the position of its lens rings and store its own lens table. When mounted to a PL-LDS mount camera, the data is transmitted directly to the camera, which calculates precise lens values, accurate to the frame. 

Option 2: External lens encoders and the Lens Data Archive
ARRI's controlled lens motors and the Lens Data Encoder LDE-1 deliver raw data about the position of the lens rings to either a UMC-4 or an ALEXA Plus module. These devices incorporate the LDS Lens Data Archive, which provides the relevant lens table used to calculate the lens value.


Through lens programming, lens tables can be generated for any lens, from vintage anamorphics to modern PL mount zooms, allowing them to be controlled -- and lens data to be collected from them -- via the Electronic Control System. 

Software Update Packet (SUP) 2.0 for the WCU-4 makes lens programming easier than ever before. The hand unit now offers a lens programming interface on its large LCD screen, so a lens scale can be programmed wirelessly in less than a minute, with no additional equipment besides the WCU-4, UMC-4 (or an ALEXA Plus or Studio camera) and lens motors. The resulting lens file is stored on an SD card, which can be taken out and reused elsewhere.

Additional features of WCU-4 SUP 2.0 include minor bug fixes and improvements made in direct response to customer feedback. Software updates such as this one permit the Electronic Control System to evolve and adapt, making it future-proof and a sound long-term investment. 


The new Lens Data Encoder LDE-1 extends the functionality of the Electronic Control System. Incorporating an encoder that delivers data indicating the position of the lens ring to which it is attached, the LDE-1 can be used in parallel with a manual follow focus unit or a third-party wireless lens control system. It allows lens data to be generated in situations when an ALEXA Plus or Studio (or a UMC-4) is being used without an ARRI lens motor or an LDS lens.

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