2 Replies Latest reply: Sep 19, 2012 2:08 PM by jmstacey
What happened to my amiga? Level 1 (0 points)

I'm working on a 90-minute film shot hot with a 50D.  It has scenes where there is natural light, photo lamps and fluorescent light. I'm an old school tape video editor gone digital, I'm used to using a TBC to do: gain, black, hue, and saturation. It's been a bear learning to use a 3 range color adjustment and it's killing me trying to color those multiple light temperature shots.


But my real problem is this:


           I discovered a problem with exporting that comes from the compression in QuickTime. Even going from 422 HQ to 422 HQ the re-compression is adding a gamma curve to everything and making the blacks darker and causing faces to shift into red more.


            I read a bunch of articles on this problem, but no one seemed to really have an answer. It seems everyone thought it was a monitor calibration issue or who knows what. The only thing to do was use my scopes and see if I can reproduce the problem there...


           So I exported a gradient fill black to white in 422HQ and when I opened it in FCP the gradient is flat on the scopes. But if I re-export it and look at it again there is a definite gamma curve on the gradient when you look at it in a scope. If you stack both clips in your timeline and do a wipe between them the difference is very clear onscreen as well. This explains why I always thought images exported from after effects, or anything that uses QT, had more contrast. I just never bothered to figure out where it was happening, I just assumed it was the programs, but it's the re-compression that does it. It’s Quick Time.


            I'm sort of perplexed at this point. I render to send to Color. Then color renders to send to FCP. After this I need to add Film grain and digital makeup artist; client’s preference on the digital makeup, I like it as is.


            Adding those effects means I need more rendering. At this point I've got two renders, each drops the mids by maybe 5 ire and the blacks by even more. My end result is not quite right. So if I compensate by making things brighter and doing an opposite gamma curve before export, I'll have no idea what I'm looking at as I do the color work.


Is this how professional colorists work? Do they make a file that looks wrong, but will look right after the final codec is applied?


Try it yourself. Make a gradient in FCP. Look at it on the scope: flat slope with no curve.

Now export it with QT and recompress it: flat gamma no curve.

Re-export it again with the same codec: Gamma has a slope toward black.


Stack them in the timeline and do a half screen wipe and you can see it clearly.


Do the same thing with a clip that has faces in it. The export creates pinkish faces. 


Am i doing something wrong? Is there a tool out there for handling this?