HDS — High Dynamic Snow


We have invited in our office in Paris, Rémy Chevrin, cinematographer, with Karim El Katari, colorist at Eclair, to share their experiences working on the film “Tout là-haut”, first feature film by Serge Hazanavicius with Bérénice BéjoVincent Elbaz and Kev Adams.

Rémy, you have pictured the great photography of this film… how did you conceived the image of “Tout là-haut” ?

Rémy Chevrin : To start from the beginning, the film was written by Serge Hazanavicius who, on top of being the film director, is a great skier. For more than 20 years, Serge has developed a strong bonds with mountain guides, including with Stéphane Dan from Chamonix (Mont-Blanc).

This friendship built over the years on ski slopes, has led them to want to tell a story happening in the mountains… This story is above all a co-written one between Stéphane and Serge, built from the conversations between two men with a passion for mountain and film making. When Serge contacted me to tell about “the big white!”, I understood this was the opportunity to picture the mountain and the snow like Besson had been filming the sea and its depths in the movie The Big Blue

We knew we had to be able to show all these qualities of snow, these different sorts of whites, showing these shades were a very important point for Serge. To conceive the image I had to listen carefully to all the words that Serge and Stéphane were using, such as : “clarity, luminance, brilliance, cotton, softness …” and also the “warmth” because there is some kind of heat in the snow. All these ways of describing it allowed us to better understand how we were going to film and how to make the best choices when filming on set.

How long did the preparation with Serge take ?

A lot of time … I first made a mood-board, the artistic document with the intentions, frame, contrasts, lighting and references. This job was approximately spread over a month and a half.

With high security constraints, what did it change for you?

On the whole I think we had 12 mountain guides within a team of 40 people in total. The Chamonix guides are great professionals, they can, for example carry in emergency 60kg on their back, with two bags at the same time, one bag at back and the other at front, and still ski without any problem. They are very impressive !

Most of the filming took place Chamonix, in the valley, in the city, on the peaks and then later in Ladakh in the foothills of the Himalayas.

To be able to do this shoot, did you take any special training?

No, all those who joined the crew had to be good skiers. Members of the team had to to be able to pass through any snow with a backpack of 20 kg and without anxiety, without the anxiety that can release some people in this type of difficult environment.

Spending days between 3000 and 4500 meters high, we all had to pass some physical and cardiac tests.

Was the film crew smaller?

No, the team was not smaller despite the extreme conditions of the shooting, in fact the people who were there were also people who were responsible for the security. We had a cameraman specialized in mountain filming and for the rest of the shots we were the ones on the set.

Which cameras did you choose and why ?

So there were many things to take into account…, so I made a list of the pros and cons of each camera. Knowing that the main advantages are reliability and compactness. Strangely, I did not spend too much time on choosing a sensor or an other, or such color space or an other, since I was carrying in my backpack a compact camera with a zoom.

The choice of the camera was quick, with a benefit for the Red weapon equipped with small angular zooms (15–40, 28–76 and 45–120), so we had three cameras with all three cameras the same setting of color rendering.

On the other hand, it we had a Red Dragon camera in the helicopter, allowing us to control of the camera with Mikaël Lubtchansky’s Foolcontrol making it possible to change all the parameters of the Red from an iPhone. And considering the extreme conditions we did not have a DIT on set.


Despite these extreme conditions you could have monitoring on set ?

I had a video assistant who made a great preparation : he managed to put together on his backpack 3 monitors one on top of the other … this superb installation with 3 videos screens out there on his backpack allowed us to view what we were filming, despite the condition. We had a basic 17 inch monitor, and two smaller ones probably 13 or 14 inches. But having these 3 monitors set-up like that, that’s what allowed us to have an image at any time by any temperature, sometimes freezing bellow 30 °.

How long did the filming last?

Rémy: We started filming on December 21st 2015, with then 2 days January 23rd and 24th 2016, and finally we shot from February 15th to June 1st. After that we also had a few days shooting in Nepal and Tibet in November.

At what stage are you in contact with Karim, to discuss “color grading” of the film?

Karim: Between the first part of shooting in 2015 and the second one in 2016 we did some tests and started to talk about colors together. The grading of dailies allowed to edit the film with the DOP’s artistic intentions. This specific color grading was then used during on the final grading by simply transferring from FireDay the meta-datas to FirePost. In the end, the film benefited from the workflow between Florine Bel (R & D engineer at Eclair), and Karim, using FireFly Cinema’s grading tools right from the start from dailies on set to post-production. This added value to the production line especially during the production and post-production stages.

Remy: The workflow was simple. We had a colorist at the lab Miguel Bejo, who graded the dailies according to the indications that I gave him. The editing room was in Paris and the team in Chamonix was getting back the graded dailies every two days.

If we talk a little bit about post-production, and that’s when Karim’s work really comes in? Were you working in the ACEs workflow?

Karim: When we did our tests with Rémy we quickly decided to use an ACEs workflow. Florine Bel had developed several “shaders” according to the sequences, depending on if we were in day / night, that could be a problem for some colors. For example, there has been some problems with some combinations of color, some skis or some cloths were too flashy or with some flares that are a little opaque.

Our engineer managed to correct them with LMT shaders, and they were integrated directly into FirePost thanks to GLSL support. We worked fully in ACEs workflow, also because our color space work was in ADX10.

Why choose ADX10 rather than for example ACEs CC?

Karim: Because I find these tools are more efficient, better positioned. Inmy opinion, it reacts more naturally, especially on the contrast, the distribution of saturation. It works much better on color selection and it also had a huge impact on color separation.

This film had the particularity of being graded directly in EclairColor HDR(High Dynamic Range). An effective grading, as in two and a half weeks everything was produced: the edit and the grading of the scenes. And the result was satisfying: the ski scenes take full advantage of the benefits of HDR. The EclairColor HDR version has a level of details on the snow that can not be reached on a standard projection. We find all the snow texture the director wanted. But things got complicated when we attacked normal calibration in SDR. The director did not find the brightness or the volume he had in mind for the snow. While on faces and comedy scenes, everything was absolutely spot on in EclairColor HDR. This phase was complex because there was a lot of round-trips between the SDR and the HDR. The normal SDR grading had to be done on several scenes.

What was really interesting and even a bit complicated for me as a colorist is that at some point Serge asked me to see the SDR version and the HDR version at the same time. Thanks to FirePost, that it was possible because the software makes it easy to change between two different tracks and thus to switch from one SDR version to the other HDR version, according to the director’s will.

The flexibility and adaptability of FirePost made it possible to work on some colors, whilst keeping the “whites” different from the rest of the image. This allowed us to refine between EclairColor HDR and the SDR.

On both versions EclairColor HDR and the SDR one, we have been using FirePost’s digital filters, there is one called “local contrast”, and in fact, it was used throughout most of the film, especially on all snow scenes. This filter helps to distinguish the different types of snows we had within the a single scene.

Allowing us to play on the texture of the image, to modify the snow accordingly and obtain a very detailed effect, with either a look like “cotton” or a “crystal” one. This setting that is native within FirePost, it is is very similar to a clarity filter that can be found on most photo editing softwares.

At the end of day, FirePost made us save a lot of time on this project.