SMPTE Q&A—Francois Helt

Shortly before the start of the SMPTE 2016 Annual Technical Conference & Exhibition, NewBay editors spoke with Francois Helt about his session “HDR Perception Challenges and Measures in Cinematographic Environment.”

TV TECHNOLOGY:What are the primary challenges of delivery true HDR to a theater? How are these being addressed?

FRANCOIS HELT: The first challenge is to get correctly lit and graded HDR content. Camera technology is already allowing this; the creative people, cinematographers and colorists especially, will become accustomed to HDR productions. The other challenge is to assess HDR rendering in projection. The technologies are not solving everything. It is absolutely necessary to understand how the audience is perceiving the content. The projection, the audience and the room environment must be taken into account.

TVT:What do cinematographers think about HDR?

FH: Frankly I do not have enough information to speak for cinematographers. I heard one interesting remark from a colorist saying that some current shots were so well done they were already easily graded in HDR. I guess that the most important factor is their personal experience of HDR rendering in theaters.

TVT: How delicate is the HDR image–in other words, how easy is it for a compromised environment to simply undo all the benefits of an HDR display over SDR?

FH: A small theater room with bright safety signs is enough to reduce perceived contrast considerably. But HDR-graded images have a different look. They will retain this look even in reduced contrast projection environment. As cinema is an evolving self-referential language, HDR-graded sequences will eventually become the mainstream look, and SDR images would have a special meaning; something similar to the artistic use of saturated images.

TVT:For the cinematographer: The transition in the ’60s/’70s from shooting for BW to color TV was rather slow–most DPs, producers and networks wanted to hold onto techniques that made the most of the limitations of BW displays, rather than abandoning those methods to make the most of what color offers. HDR allows for both subtle and extreme lighting techniques that simply won't translate to SDR. Is there some tipping point to look for where DPs should ignore how something plays in SDR and just shoot for HDR?

FH: This is a difficult question. The answer will vary with distribution channels, content type, financial and even cultural motives. In short and for broadcast, sport is the content that will make the most use of HDR quickly; but a good enough SDR rendering will be important, at least to understand the action because HDR displays should not outnumber SDR display soon.

For cinematographic work, my guess is that the number of cinemas offering a good HDR experience will play an important role. Studios are already used to produce many different graded versions of a movie, but there’s a general trend to try to reduce this number. So this would favor mixed productions for a time.

Interestingly cultural factors could play a role. I am thinking about the difference between entertainment and “cinema d’auteur.” HDR entertainment needs to provide a real high-contrast experience and would require enough theaters with corresponding projection specifications. So they will need to push theater owners to do the upgrade. On the contrary some cinematographers may be more interested by the linguistic aspect of HDR-graded sequences and would use HDR faster.

TVT:What should come first, standards/recommendations for theatrical environment specs or for HDR projection specs?

FH: In my opinion it is clear that theatrical environment is more important. It is necessary to ensure that the audience is having a good enough perception. Financial considerations should also be taken into account when readying all the theaters for HDR.

Francois Helt serves as chief scientific officer of Highlands Technologies. His current interests include visual perception models, measurement theory and philosophy of information.