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nasty gamma bug survey

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Michael Rampe
nasty gamma bug survey
on Oct 15, 2009 at 5:21:09 am

Hi all interested readers,

I have been investigating the nasty gamma issues present in FCP/QT/AE/COLOR for over a year now and have made an interesting little discovery.

Recently, I have taken on the job of editing a short film that was shot on the canon 5D. I took all of the original files (which are .mov wrappers with H.264 essence at 1920X1080, 30fps) and converted them to Prores4444 using compressor. They look the same in Quicktime. They look the same in FCP. The Prores4444 looks the same in color and After Effects. They look the same when round tripping back to FCP from Color and After Effects. This was all done on my work machine (8 core MACPRO, OSX 10.5.8, QT 7.6.4, FCS3, CS4 AE, GEFORCE 8800GT)

Now to the discovery.

I took these files home to my home machine to do some more work. THE GAMMA SHIFT BUG REARED ITS UGLY HEAD. The original looks right in all programs (QT, FCP, AE, COLOR) The Prores4444 files looks washed out in ALL PROGRAMS.

All specs are exactly the same in all regards except it is a Quad core MACPRO and it has an ATI X1900XT graphics card.

This leads me to the conclusion that it is either the number of cores (highly unlikely) or THE GRAPHICS CARD. I then did some searching on this board as well as others (again) and realised that most users experiencing this shift have ATI graphics cards.

On to the survey:
If you are experiencing this problem as many users are, what type of graphics card are you using? Also, if you are not experiencing this problem, again, what type of graphics card are you using?

NOTE: this survey is not specifically related to the H.264 gamma shift on OUTPUT from FCP or QT etc. (although it may well be....)

SECOND NOTE: please DO NOT bang on about "using a fully calibrated broadcast monitor" as this is also not related to this issue.


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Rafael Amador
Re: nasty gamma bug survey
on Oct 15, 2009 at 6:16:58 am

[Michael Rampe] "I took these files home to my home machine to do some more work. THE GAMMA SHIFT BUG REARED ITS UGLY HEAD. The original looks right in all programs (QT, FCP, AE, COLOR) The Prores4444 files looks washed out in ALL PROGRAMS. "
Hi Michael,
This only tells me that you may have your home screen at 1.8 while your work place screen is at 2.2.
The problem is when each application (QT, FC, Compressor, AE,..) display a different gamma, or in processes that produce gamma shift without reason.
rafael



http://www.nagavideo.com


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Michael Rampe
Re: nasty gamma bug survey
on Oct 15, 2009 at 6:32:05 am

both screens were set to 1.8 gamma.
Just set home machine to 2.2... same result.

To repeat:
At work, ALL programs display the footage correctly.
At home, ALL programs display the footage incorrectly.
The ONLY difference between the two computers is the chipset and graphics card.

I have also just tested the footage on Snow Leopard with an ATI X1900XT card.... same result.

BTW, do you experience this problem? If so, what graphics card do you have.

Michael


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Michael Rampe
Re: nasty gamma bug survey
on Oct 16, 2009 at 2:29:53 am

just tried the work computer at 1.8 and 2.2 and the converted footage still looks right either way. (It was originally set to 1.8 anyway)

To further support my theory of the graphics card being the culprit, read http://en.wikipedia.org/wiki/Core_Image

IT IS THE GRAPHICS CARD THAT PERFORMS THE GAMMA ADJUSTMENT.

Anyway, I am still smiling that I have access to a MAC that truly displays WYSIWYG in all programs with Quicktime footage. It has been a while since this was the case....


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Andy Mees
Re: nasty gamma bug survey
on Oct 16, 2009 at 3:09:36 am

Thanks for posting your findings Michael
Andy


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Harry Powell
Re: nasty gamma bug survey
on Nov 8, 2009 at 9:44:14 pm

Thanks from me too!

Would be nice to hear from anyone else who can reaffirm your experience.. before I rush out and buy a new graphics card(?)

Using FCP 6.0.6 and have an ATI Radeon HD2600 in an 8-core 2008 Mac Pro (Leopard). Would any non-ATI card definitely solve the gamma problem I wonder? Any recommendations?

I have been trying to find a solution for a long time and many threads with different ideas end inconclusively, and/or their suggestions haven't worked for me.

I'm also getting more than a simple gamma shift, as described by Chris Wiegand here http://forums.creativecow.net/thread/8/982913#982913
i.e. I'm getting some extra green too!

And must admit, even the basics are confusing me. For example (maybe slightly off topic), when using 'Display Calibrator Assistant' - it first instructs me to push contrast to maximum setting. Am I meant to leave it this way after calibration is finished? Also, the 1.8/2.2 gamma settings option comes up as one of the final steps. Surely this should come up near the start, before you do all that manual fine tunings? I just don't get it. And which gamma setting should it be for FCS work anyway? Would it be the same for DVD authoring and web work?


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