It’s not everyday that we get to speak with a physicist and discuss his work on products that are high-end tools for our industry. We were lucky enough to have this opportunity recently when we spoke with Benjamin Voelker, Optical Designer/Simulations at Carl Zeiss AG.
Los Angeles Post Production Group: Please tell us about the type of work you do for ZEISS and how you got into this field?
Benjamin Voelker: Before joining ZEISS, I have worked in various fields, including nanotechnology, material science and mechanical engineering. As a trained physicist, the professional focus of my work was always on numerical modeling, i.e., creating numerical models that describe complex physical models, to simplify them and to use them for optimizing problems. Apart from work, I developed a growing interest in photography over the last 20 years. What started as a hobby quickly grew into a passion during a two-year research stay at UCSB, when I became serious with landscape photography and astrophotography.
Traveling around the world to find dark night-skies and places with great wilderness is what makes me happy. So, when I joined the ZEISS Consumer Optics Business Group in 2013, this was a unique opportunity for me to bring together work and hobby. Today I’m a senior expert in the design of optical coatings and the prediction of ghost and flare in all kinds of optical systems. Working together in a team with optical designers and mechanical designers, we develop new ideas and new optics to provide cinematographers with the tools they need.
LAPPG: Can you tell us about the idea behind the ZEISS Supreme Prime Radiance Lenses, which were released in 2019 as well how they were designed and created?
BV: The idea behind the ZEISS Supreme Prime Radiance Lenses is pretty unusual. Normally, modern optical systems are designed and optimized in a way that the image is clean and flawless, with as little “unwanted” light on the sensor as possible. Unwanted light can originate from light being scattered from mechanical surfaces of the inner contour of a lens or being reflected multiple times on optical surfaces before it unintendedly reaches the sensor plane and causes unwanted contrast loss and ghosting artifacts in the image. To tackle this basic problem in optics, as far back as 1935 engineers at ZEISS developed the T* optical coating, that literally makes glass invisible. This technology has been optimized ever since and enables us to offer optics with great neutral color rendition, the highest possible contrast, and a minimum of ghosting artefacts.
However, when me and my colleagues talked to cinematographers, we felt that some of them long for a different, less clean and perfect look. Some go for vintage lenses, with the problem that these lenses are rare and difficult or nearly impossible to service in case they fail. Others use optics with some completely uncoated lens elements; this introduces very strong white ghosting artefacts, which are completely uncontrollable, destroy the image contrast and at the same time reduce the available signal light that forms the image.
The idea behind the ZEISS Supreme Prime Radiance Lenses was to create an entire modern lens family that offers a consistent characteristic look while overcoming the difficulties and limitations just mentioned. The lens family, covering focal length from the super wide angle 18mm to the 135mm telephoto focal length, offers pleasing and controllable lens flare that can be used as a visual story-telling element.
The first major challenge was to introduce consistent lens flare over the entire lens family. Lens flare is light being reflected multiple times on lens surfaces before reaching the sensor, so if you change the properties of a single lens surface (e.g., by applying a different optical coating), the effect on lens flare is huge. By means of trail-and-error it would have been impossible to get lens flare consistent over the whole product family. Instead, we used virtual prototyping: for hundreds of combinations, the lens flare was computed in simulation models, until we found the perfect combination. This simulation was the most demanding I had done so far; on a single state-of-the-art CPU it would have been running for almost half a million hours, that’s more than 50 years!
The second major challenge was to develop a new kind of optical coating especially for the ZEISS Supreme Prime Radiance Lenses, the so-called T* blue coating.
LAPPG: Can you explain what the T* blue coating is and how it is used?
BV: It is a new kind of anti-reflective coating design that introduces bluish lens flare of a carefully chosen intensity level, while keeping the resulting overall image contrast intact. It makes sure that the maximum apertures of the ZEISS Supreme Prime and the Radiance lenses are on the same level, at T1.5. As a benefit, it introduces a slightly warmer color rendering tone when compared to the original ZEISS Supreme Prime Lenses, and great care has been taken to avoid a green or magenta color tint on the image. The T* Blue coating on the ZEISS Supreme Prime Radiance Lenses makes them a versatile tool, if you don’t want flares to appear in a certain scene you just need to flag the light, but you still will have that nice warmer color tone.
LAPPG: It seems that 4 more lenses have been recently released in this collection. Can you tell us about those and why they were added?
BV: After introducing the initial set of ZEISS Supreme Prime Radiance lenses in 2019, we received very positive feedback from our customers. Meanwhile, four more lenses had been added to the ZEISS Supreme Prime family: the T1.5/18mm, T1.5/40mm, T1.5/65mm and T1.5/135mm. Immediately after we launched the first wave of ZEISS Supreme Prime Radiance lenses into the market, we started to develop a Radiance-Version of these four focal lengths. They perfectly round off the ZEISS Supreme Prime Radiance lens family, which now perfectly matches the ZEISS Supreme Prime lens family. As before, greatest care has been taken to reach a consistent flare look throughout the whole ZEISS Supreme Prime Radiance Family. A number of productions using ZEISS Supreme Prime Radiance Lenses are already available, you can find a list of trailers here. I’m amazed what cinematographers are getting out of the ZEISS Supreme Prime Radiance lenses, and how subtle they can use the lens flare to create a unique look. To me, there’s nothing more rewarding than watching such a production in the evening with my family and knowing that I have been part in making this look possible.
LAPPG: Does the eXtended Data Technology exist in the ZEISS Prime Radiance lenses and if so, can you explain a bit about how that technology works?
BV: Yes, ZEISS Supreme Prime Radiance Lenses possess Extended Data Capability just like ZEISS Supreme Prime Lenses. In short, they possess all the features of Supreme Primes but with the addition of controlled lens flares.
Extended Data or in short ‘’XD’’ is a unique technology, based on /i Cooke Metadata with the added benefit of live Shading/ Vignette Data and Distortion Data, which is useful for VFX to determine the Vignette and Distortion of a lens before work can begin. Each lens is individually profiled at the factory and the data is saved on the Lens itself which in turn can be viewed/ accessed when connected to an Extended Data compatible product. Eg: Sony Venice (PL Mount), RED DSMC2 Cameras (PL Mount), DCS Film, Factory Optic SynchroLink. To learn more about Zeiss Extended Data, follow this dedicated link to the Zeiss Extended Data page, where you will find a wealth of information, white papers, tutorials, guide downloads etc.
LAPPG: What are you most excited for in the world of high-end cinema lenses? Is there anything on the horizon that you can tell us about?
BV: It has been really interesting to see the adoption of Full Frame and Full Frame Plus Cameras and Lenses over the last few years in the industry. It’s rewarding to see the great reception we’ve had for our Supreme Primes and Radiance Lenses of course! Also, the evolution and use of advanced Metadata for VFX has come a long way and the fact that we are communicating with all the key stake-holders in every part of the chain goes to show that every individual involved is interested in contributing towards the betterment of the products or current workflows. As for telling you about anything on the horizon, we are a manufacturer and we are always creating something new and interesting!