Gamma shift when exporting Images Sequences / Quicktimes from FCP

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Level 1

0 points

Gamma shift when exporting Images Sequences / Quicktimes from FCP

Problem : Capture from Digibeta into FCP (Uncompressed) via Aja....export the clip (either on the timelime or direct from the bin) using Export>Using Quicktime Conversion to a tiff seq. Import tiff seq into Flame...the Gamma has been shifted and is incorrect.

If I capture from tape, edit,then lay back to tape the gamma is fine.

The problem only occurs when exporting via Quicktime.

Any idea how to correct this unwanted gamma offset when exporting from FCP to tiffs?

This in not about my screen Gamma setting...it's the actual tiffs that are being exported, loaded into Flame and being checked on a fully calibrated Grade 1 broadcast monitor....I'm checking the orig frame on tape against my export on both Flame and Backdraft and the exported tiff is definitely wrong.

Any ideas appreciated,

Thanks

Geoff

G5, Mac OS X (10.4.10), AJA

Posted on Oct 22, 2007 7:28 AM

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Answer 1

JR2010

Level 1

0 points

Nov 26, 2007 1:40 PM in response to G-Free

Getting the same thing, makes it pretty hard to color correct. Would love to know why FCP is doing this ???

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Answer 2

Nov 27, 2007 1:15 AM in response to G-Free

I've been getting the same problem for months , I tried to export still images (tiffs) and each image came out much darker than it had been in FCP timeline no matter what program I used (Photoshop Elements mainly).
I also tried to get info on this a while back , but to no avail.

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Answer 3

Nov 27, 2007 11:07 PM in response to G-Free

Apple in their "wisdom" has set up FCP to "correct" between video-standard 2.2 and Mac-centric 1.8 gammas during import of stills or export to stills. Ostensibly this allows the stills to display the same on a Mac screen at 1.8 gamma as they do on the video screen with gamma 2.2.

So, you'll want to add a gamma correction of 0.8181... when exporting to still files and 1.2222... when importing from still files; 0.82 and 1.22 are what I use in FCP's gamma corrector. Chris Meyer suggests 1.228 and 0.824 in After Effects; not sure why his values differ in the third digit.

Note: in FCP 6, I see, there's an option (FCP > User Prefs > Editing > Imported Still/RGB Video Gamma) to change the gamma assumptions for imported stills and RGB files. If you change it to 2.2 prior to importing stills, it seems to work fine (you can also change it after the fact in Item Properties). However, it doesn't seem to have any effect on exports--I still have to add a gamma correction to exports. 😟

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Answer 4

Soy-yo

Level 1

5 points

Nov 28, 2007 8:51 AM in response to G-Free

Hi Geoff,
Apart of the issue of the gamma, that Adam has already answered, I would like to point to your workflow. There is any reason why you can not bring 10b Unc YCbCr from FC to Flame? I think that is a better option than bring the 8b RGB .tiffs, mostly if you have used QT Conversion. Qt Conversion is probably the worst available option.

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