Customized lenses for Netflix's "Barbarians"

Set around the Battle of the Teutoburg Forest in 9 AD, when Germanic tribes halted the northern spread of the Roman Empire, "Barbarians" is a six-part miniseries produced by Netflix and Gaumont Germany. Seeking a bespoke look that would emulate the feel of vintage lenses without creating difficulties for the many VFX shots, cinematographer Christian Stangassinger turned to the lens experts at ARRI Rental to detune and modify ARRI Master Anamorphic and Ultra Prime lenses for large format. He speaks here about his experiences with lens customization, digital look augmentation, the ALEXA Mini LF camera, and HDR grading.

What made large format right for this show?

Large format is an impressive format; the shots gain a new dynamic and depth. People and objects can be spatially delineated much more clearly, allowing a more powerful 3D effect. The results are really significant, especially in the shorter focal lengths, which I love. The larger sensor and higher resolution make the images strikingly realistic, and the image-noise behavior is way better in the low light range, which can be very helpful at night and save costs on large locations. 

On "Barbarians" it was clear that we would be shooting everything on location. That can quickly become very expensive and technically complex. A key part of my lighting concept was to use real fire to light parts of each shot. I wanted the warm color of the fire as a contrast to the cold moonlight, so I had to make sure I didn't overexpose the fire and turn the light white. I needed a camera that could reproduce the high contrasts we required. Large format is really good at that, and in particular the ALEXA LF is quite simply unbeatable, as my tests showed. With the LF sensor you can work with underexposed areas in the DI grade without any major problems. 

You worked with ARRI Rental to detune Master Anamorphics and Ultra Primes. How did this come about and what look did you achieve? 

A lens gives a scene its soul. It's a subtle stylistic device that significantly influences the viewer's perception. So much of a look depends on which lenses you choose; that's why I test in advance for every new project, in order to find the right lens for the desired look. Sometimes testing even helps me to define the look more clearly, or gain a better feel for it. 

Large format was totally new for me at the start of the project, which is why I tested so many different lenses, both anamorphic and spherical. I was drawn to anamorphic, but there were very few anamorphic lenses at the time that were suitable for large format. After some tests, Manfred Jahn from ARRI Rental Munich suggested enlarging the image circle of ARRI Master Anamorphics so they would cover large format. Because those lenses were too clean for my purposes, the plan came about of also detuning them to lend them a bit more character. Together with Christoph Hoffsten from ARRI Rental Berlin, I defined which changes were to be made to the look and the technical options for doing so. Christoph is a real expert for special requests. With his know-how it was possible to technically change the look of the Master Anamorphics.

What was important to me was to get the lenses "softer" and to have the focus falling away to the edge of the frame, along with a slight vignetting effect. I also wanted to vary the flare behavior. I'd like to have increased the distortion even more, intensifying the bulbous effect of older anamorphics, but it wasn't possible. Fortunately, our colorist Florian "Utsi" Martin from ARRI Media had created digital setups of a range of different anamorphics. At the start of the color grading, individual elements of the digital lens setups were inserted into the picture to add the missing anamorphic characteristics. In this way I could create the desired field curvature digitally and make the images even softer where I wanted. That gave me the perfect lens; one that was technically clean enough for the many VFX shots, while at the same time retaining the classic look of an older anamorphic. 

Were there challenges to working with detuned glass?

It was relatively uncomplicated to shoot with the detuned lenses. Some of them did have their more specific character, but we labeled them so I always knew which lens to use for which shot. I was familiar with the characteristics of the lenses thanks to all the testing I had done, and I knew exactly what to do at any given time to prevent optical problems. Of course, you do have to be careful when working with detuned lenses. It's a bit like using vintage lenses -- you have to study the lenses beforehand to learn their respective strengths and weaknesses. 

It was important to have a consistent look across all lenses, because only then could I employ any focal length at any time. Christoph had to work manually on each and every element in order to ensure a look that was always as identical as possible. He did an amazing job adapting the Ultra Primes to the new look of the Master Anamorphics. In the end, he detuned four sets of Master Anamorphics and about three sets of Ultra Primes. A lot of work and a whole lot of lenses! 

This was one of the first projects to use the ALEXA Mini LF. Why did you choose it and how was your experience with the camera?

Yes, we were one of the first teams to film with the ALEXA Mini LF. I'm kind of proud of that. I've always preferred ARRI cameras and have filmed nearly all of my projects with them. After carefully testing large-format cameras, the ALEXA LF was by far my favorite. It's really impressive in terms of contrast ratio, low light handling, and color reproduction. Sadly the ALEXA LF wasn't ideal for this project due to its size, but it wasn't known if the smaller and lighter Mini LF would be available in time. Happily, ARRI liked the project and although the Mini LF wasn't on the market when filming began, they provided us with four pre-production models -- a really great service that I'm truly grateful for! 

The ALEXA Mini LF is only minimally heavier and bigger than the ALEXA Mini. Alongside the great pictures the larger sensor provides, it was also the best solution to our technical needs on set: easy to rig, quick and easy to use in a gimbal, TRINITY or Steadicam, and not too heavy for complex handheld sequences. 

Had you worked in HDR before this project? 

"Barbarians" was my first project in HDR. I'd looked into HDR before, but only in the form of smaller tests and the odd talk with a colorist from time to time. On "Barbarians" the decision wasn't made until postproduction that the project would be finalized in HDR. The workflow on set was arranged for SDR, so when we began grading, I had to depend on Utsi. He is a really great and experienced colorist, who was also involved in the development of the ALEXA Mini LF. I had put together the LUTs with him for the show in advance, so he knew exactly what was needed to create the desired HDR look. 

If you had known about the HDR deliverable from the beginning, would you have done anything differently on set? 

Oh, definitely! If we had known during filming, I would probably have set up the lighting differently in some places. It wouldn't have been so necessary to brighten things up as much. I would have lit bright areas like windows, fires, and faces differently. I would have positioned really bright elements like torches in other places sometimes, because their brightness can quickly become a disturbance in HDR. But in the end, it wasn't that dramatic, because we could change things during color grading. Fortunately I had enough time to do the grading, which isn't always a given nowadays. 

Can you describe the feeling of walking onto set on the first day of shooting?

I'm always a bit nervous before the first day. I often dream of the planned camera setups in the nights beforehand. I look at them like an audience member, and if they don't feel right, I change them. It's an important process and helps me get a feel for the scenes, which can be helpful when decisions have to be made ad-hoc on set. Ultimately, though, I'm happy that filming is finally getting underway after a long preparation, so the first day is always something special. For me personally it's important that the mood on set is good and my team gets along, and we are all on an equal footing. In the end, we're all here to make a vision become reality. Making a film or series is a creative process that involves many different people, so I really like the working environment to be pleasant.