[Tig] LUTs from production - how useful are they?

Craig Leffel craig at optimus.com
Fri May 7 04:54:52 BST 2010



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Really, are people not using production LUTs, or is this somehow a delicate
subject or something? I would have thought this was the ideal place to ask the
question...

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I started to answer this question twice Bob, and realized that I don't get many "official" LUTS sent to me. 
I get a lot of stills, QT's, and rsx files sent to me as reference, and it works pretty well.

The biggest trick about LUTS is that in their purest form they are color space conversions, and not really meant to be used creatively... IMHO.

So, when everyone started using Cinetal monitors on set and were dialing in Rec709, Rec601, etc - or the cameras were recording Log, but actually displaying Rec709 out their video port... 
it became a huge problem for us to duplicate what was being seen on set. It was very unclear what particular Rec709 setup the Cinetal had in it, and most of the manufacturers I use blanched at the idea that I needed a Rec709 LUT that I could drop onto any Phantom, Red, ArriD21, etc. .dpx Log file conversions I had, and be sure I was replicating - as a starting point - what was being shown on set.

It's honestly still a problem, but most creatives involved in the pipeline have figured out the tolerances and intolerance in the paths. I use a number of LUTS in Baselight, but they're custom made and called Truelights.
They can be used on set, as Filmlight makes an onset grading tool... but as you've mentioned, so does Iridas, Gamma and Density, Davinci, etc. For those kinds of jobs, where color correction is being viewed critically on set, it seems to me that the only real choice is to find a house compatible with the tools you are using on set, and pass the grade files along... because, when done right, the grade files are valid, and more useful than just a LUT conversion from Log to Lin or from one Log space to another. If you consider monitor LUTS in this conversion as well - LCD, Plasma, CRT, Projector - the whole thing becomes extremely unpredictable and almost useless. I will take a still as a reference any day. I hardly ever start out a session with a Rec709 LUT in place, and I never use that LUT in my Grade stacks. I treat Log files like I would view film, and I've come to be very familiar with what's in the capture based on what I see in Log. I almost always prefer to have as much detail as I can, shy away from canned LUTS, unless I'm trying to emulate something like a print stock, print look, chemical process or actual color space conversion.

Good luck -


Craig Leffel
Senior Colorist
Optimus




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