Saturday, 7 June 2008

Achieving a 4k workflow

I’ve just had a very interesting experience grading some 4k Red footage (my Yosemite Project) in Pepper’s Grading suite in Soho, London. For the first time in the investigation into HD I felt I was conducting research.

For a start the comment from the days work that rang through came from Jet Omoshebi, a well respected colorist on the London and European scene. When asked compared to importing film at 4k, how did red 4k footage compare? She answered: In the short time she had to play with the footage she had not come to the end of its latitude which was the case when grading standard HD footage. This to me was revolutionary because it means that the sheer limitations of electronic cinematography colour space, which was the basic problem in grading, was not there at this level of electronic cinematography.

The other thing that rang out from working with 4k was the fact that all future handling of data is limited by its size and the pipelines we can push it through - and, importantly, the physics of the medium. WHat that means is that we have to seriously start thinking of using metadata to control the oceanic drifts of data around the systems we use. To continue the seafaring metaphor: As we increase our demands on the information that describes what lies in our field of view through the camera, or mobile scanner (as Tim Sassoon, the British yet-based-in-Los-Angeles-grader, calls the modern electronic camera), then the super tanker of data - which used to be through compression a small boat - needs to be steered through its various incarnations by a little tugboat with all the relevant information about it. How big it is, what it’s supposed to do, whether it’s supposed to look like a red supertanker, a blue supertanker etc. Time to ditch the metaphor which is becoming preposterous.

So in the grade, on a digital vision Film Master, which can handle 4k data, we were actually using RedCine to output Redcode in Log mode as opposed to Linear broadcast space which would be limiting and then made 2k DPX files. The Film master was outputting through a 2k Barco Projector. We occasionally looked at 4k DPX files and of course could only see a quarter of the image - but the detail was incredible. Back in 2k we graded and the we the take the metadata - the instructions about how the footage should look - out to the 4k render path.

A note here is that a lot of facilities have a raid array set up for Broadcast ad HD specs and of course 4k needs about 900 Mbs - so in a protected raid you really need 1800 MBs which halves when in it’s protected mode. At home I have a raid that runs around 485 MBs - unprotected - but it’s so cheap I could buy another and do the backup myself through automating via the Mac. I used Redcine to select takes and final cut to import proxy files to edit what I wanted - this was a kind of sketch pad prior to the proper grade.

So, eventually when the 4k DPX files are thoroughly rendered we can either output for 4k Projector or apply a Lut for the particular stock and output to 4k film. The only difference in our experience was that we didn’t have the 4k projector to view through which of course may have influenced some decisions.

I guess you had to be there.

That’s the thing about all of this knowledge, outside of a theoretical understanding, you actually have to do it yourself to truly understand what’s happening and if you have that understanding you can think of new ways to create new pathways that might be better than the accepted ways of doing things which might in fact derive from somebody having had use of a particular piece of kit and the idiosyncrasies of the kit influenced thoughts about what was a ‘good’ idea which later proved a bad idea. In a sense, people in high level post production facilities are the best placed to do the experiments. Rendering though is a key issue and a piece of kit like the Film Master has 17 processors. No doubt more processors will be added and other companies will have other solutions and eventually rendering will occur faster than the delivery to the display device creating a ‘real time’ experience.

Incidentally, the grade Jet achieved on the shots of Yosemite - especially when we finally drained the colour to imitate the famous Ansel Adams picture - were phenomenal.