DSLR Workflow to Avoid Gamma Shifts?

R

robotsound

Well-known member
Has anyone figured out a way to import and export DSLR footage (without AMA) and get the output to look identical to the input?

The goal is to import a single Canon DSLR clip, immediately export it, and have them both look identical. If this can be achieved, then the Avid won't mangle any footage, and just pass it straight through. Should be simple, right?

Here are the things I have tried systematically so far. Each of these results in footage that looks different than the original (when viewed in both QuickTime 7, with the Final Cut Pro Compatibility setting checked, and QuickTime X).

Set project to RGB 709 / Import clip as RGB / Export clip as Quick Time Animation RGB
Set project to RGB 709 / Import clip as RGB / Export clip as Quick Time Animation 709
Set project to RGB 709 / Import clip as 709 / Export clip as Quick Time Animation RGB
Set project to RGB 709 / Import clip as 709 / Export clip as Quick Time Animation 709

Set project to YCbCr 709 / Import clip as RGB / Export clip as Quick Time Animation RGB
Set project to YCbCr 709 / Import clip as RGB / Export clip as Quick Time Animation 709
Set project to YCbCr 709 / Import clip as 709 / Export clip as Quick Time Animation RGB
Set project to YCbCr 709 / Import clip as 709 / Export clip as Quick Time Animation 709

I've also tried exporting to DNxHD in a QuickTime wrapper (the only choice for DNxHD it seems), and bypassing QuickTime entirely and exporting to a sequence of PNG and TIFF files, all with similar results. Some export closer to the original than others, but none of them match entirely, and they're all over the map.

Surely I can't be the only person who has ever tried to do this.

Does anyone have a reliable non-AMA Avid workflow for working with Canon DSLR cameras?
 
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Do you have perian installed? It's been known to mess with AVID's AMA feature. I haven't done any work with DSLR footage directly in AVID yet. Personally I transcode everything off the bat into DNxHD115 in After Effects. The resulting files do not have a gamma shift. Then I import those files into AVID and never go back to the originals.
 
I avoided AMA altogether, preferring to try things the traditional route. I don't mind transcoding, and I want the rock solid media management and time tested workflow.

What did people do in Media Composer 4? Just live with the gamma shift? Somebody has to have solved this. Right?
 
An update.

I tried some import/export tests again, but this time used After Effects as the method of measurement. I would load the original Canon camera file in on the first track in After Effects. I would import the camera file into the Avid, export it again, and import the resulting file into After Effects. I would then run a difference between the two channels. Color management in After Effects was turned on (I tried Rec 709 full swing (not 16-235) and also the universal gamut).

When I used After Effects to measure the differences, I noticed that there was no gamma shift between the files. I also noticed that all of the files the Avid exported had ICC color profiles, while of course the files from the Canon camera did not.

I have taken away two points from all of this.

1) The Avid seems to be at least pretty OK with regard to color accuracy, and possibly excellent.
2) The QuickTime player (either 7 or X) is a terrible way to measure anything whatsoever.
3) After Effects, and ICC color profiles, are your friends.
 
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I don't know why you don't consider AMA - not for direct access editing, but for access/transcode with more control and faster processing times. There have already been responses here for things like Perian as well as QuickTime is not the greatest container format for codecs and always wants to change things in what it thinks looks better... Also not that roundtripping can introduce some small changes as there can be rounding in RGB to YUV, etc. seeing as DNxHD is a Rec.709 codec. RGB is a bit of a misnomer in the import - it really refers to levels being full range or graphic levels (0-255) versus video levels of 16-235.

AMA source settings allows you to select: do nothing, make video range, or expand depending on the levels of the source footage. The histogram has white bars to show you where 12 and 235 video levels fall.

Once a clip is AMA linked, you can select transcode to a DNxHD codec of your choice and it will do so 2x faster than an import as it uses all the cores in the CPU versus the older import code which is not multithreaded.


Michael
 
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