Is it true that color corrections and grading should never be done on proxies?

[Duke Sweden]

I would guess that you’re trying to correct and grade a clip with less data to work with. You might get it perfect after much tweaking only to find that it looks completely different on the original file.

For me, doing anything on the proxy file just bogs everything down. I get a lot smoother workflow working with the original files, for some reason. And I’m talking 4k mp4 files as opposed to proxy files of 720 SD mxf files. Huge difference, yet the 4K files run much smoother for me. Go figure.

[Yair Bartal]

Thanks Duke,
Concerning “you’re trying to correct and grade a clip with less data to work with”, I would guess this general claim holds for many other effects, so I’m not sure how the lumetri color effect is different.

[Duke Sweden]

I guess there’s a difference between adding an effect and actually changing the color information in a clip. Mind you, I’m pretty sure working with proxies wouldn’t be such a major new PPro feature if you couldn’t do much with them. As I said, I’m just a hobbyist. I’m hardly the last word on any subject here. That’s just my opinion, and my opinion usually draws out the guys who really know what they’re talking about 😉

[Alex Udell]

I think the answer depends on a couple of things…

are the proxies only a temporary step in the workflow, or are they just a step down because the full resolution is to difficult to play….or take of too much space to keep local online all the time… in other words…will you be switching back to source for final output?

additionally…

what has happened to the color space in the proxy conversion?

as Duke was indicating…

if your proxy is visually different in color than the source….then grading would be pretty useless…I’m sure Lumetri is not yet smart enough to adjust itself dynamically and understand your intent when changing between the proxy color space and source color space….

You can make a lot of editorial decisions with low visual quality proxies….but I assume grading probably ought to be handled when you are at least seeing common source color.

that’s my long winded response. ?

cheers…

Alex Udell
Editing, Motion Graphics, and Visual FX
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[John Pale]

Sometimes color grading can introduce visual artifacts if done to an extreme (especially in the blacks). If you are grading low resolution proxy clips, you would not know whether the artifacts are from the color grading or compression artifacts inherent in the source material.

[Tero Ahlfors]

[John Pale] “Sometimes color grading can introduce visual artifacts if done to an extreme (especially in the blacks). If you are grading low resolution proxy clips, you would not know whether the artifacts are from the color grading or compression artifacts inherent in the source material.”

And if you’ve done any secondary color correction (keys, curves) then there’s a chance those will not work correctly when you switch to the original.

[Walter Biscardi]

You can color grade proxies all you want, it’s just that any effects, color grading or otherwise, introduces more noise and degradation to the image. But this doesn’t matter since you’ll be replacing the proxies with your full resolution images before you output and you should be able to transfer all your color grading information over to the full resolution footage as well.

Walter Biscardi, Jr.
Editor, Colorist, Director, Writer, Consultant, Author, Chef.
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