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Alternating colour shift on converting EOS7D H.264 to ProRes HQ

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Kenneth Scicluna
Alternating colour shift on converting EOS7D H.264 to ProRes HQ
on Mar 5, 2010 at 7:12:07 pm

Another gripe with the 7D.

When converting footage from H.264 to ProRes HQ (FCS2 system, conversion done via Compressor) we've noticed that some clips have an alternating shift in colour.

What I mean is that on playback the clip starts off ok, then suddenly shifts colour slightly, and after a while shifts back again, and then the cycle is repeated.

We also desaturated the footage with FCP6 and the shift then manifested itself as a slight difference in brightness.

When filming, camera was on Manual with a set White Balance.

Any clues on how to fix this issue?

Thanks all.
k


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Robbie Carman
Re: Alternating colour shift on converting EOS7D H.264 to ProRes HQ
on Mar 5, 2010 at 9:38:08 pm

does the original footage exhibit this shift? Where you shooting 720p60? I've never seen it on my cameras but the other day I was helping a client who had shot probably about 50min of 720p60 on the 7D all with in a little of an hour and the camera got the temperature warning several times. Lo and behold the footage had the shift you were are talking about.

Robbie Carman
----------------
Colorist and Author
Check out my new Books:
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Jonathan Ziegler
Re: Alternating colour shift on converting EOS7D H.264 to ProRes HQ
on Mar 5, 2010 at 9:49:11 pm

Do you, or anyone else, know the time limit (generally, I know there's several factors that can contribute) before you start seeing heat issues? Anyone have a way to reduce heat quickly without damaging vital electronics?

Jonathan Ziegler
http://www.electrictiger.com/
520-360-8293


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Ian Clark
Re: Alternating colour shift on converting EOS7D H.264 to ProRes HQ
on Mar 6, 2010 at 4:51:02 pm

Kenneth,

Does the color shift occur only after you've transcoded to ProRes (not visible in the source clips)? On one project earlier this year (after shooting for close to an hour under varying lighting) I ended up in a room with fluorescent overheads and had a problem with horizontal banding in my image- approx. 8 bands stretching across the screen in a pattern of light, dark, light, dark, etc. Possible overheating or perhaps the shifting color temperature of fluorescent lighting and as a result my sensor reacted in such a way?

Doesn't sound like what you're experiencing, but figured it was in the same vein of possible overheating issues. Good luck-

IAN CLARK | http://www.incproductions.org


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Kenneth Scicluna
Re: Alternating colour shift on converting EOS7D H.264 to ProRes HQ
on Mar 8, 2010 at 8:59:53 am

Hi All

thank you so much for your contributions.

In answer to the various questions.

The camera did not overheat -- the shots were taken as the camera was switched on.

The original footage did not exhibit the shift.

The footage was filmed at 1080p 25fps.

We ran a test, selecting the "Enable 4:4:4 Chroma Filtering" option when encoding to ProRes(HQ) and it looks like it may have cured the issue...


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