Gamma Shift in Pro Rez / FCP

[Tim Naylor]

I shot a feature at 4.5k 2:40. Transcoded dailies to Pro Rez 422 half rez (HQ). The default size without letterbox came out to 2240x960 (no letterbox). I'm cutting some clips together on FCP for my reel and promo piece. The problem I'm having is when I pause the timeline the gamma shifts to noticeably brighter and much darker when I press play. When rendered, exported to FCP movie and played back in QT, the gamma/brightness almost matches the paused gamma/brightness in FCP. I'm using FCP 6.06.

As a test, I dropped my dailies into a 1080 16x9 timeline, letting FCP automatically re-scale and letterbox the clip. No gamma/brightness shift at all.

So is this a problem with the non-standard format (2240x960)? If so, is they're a setting to override it. As of now, without a fix, the only viable solution I see is offlining in the current "native" timeline and then dropping it in the 1080 16x9 timeline for color correction. I was hoping to avoid this for a variety of reasons, namely avoiding letterboxing.

Any notions from the more post savvy folks here. BTW, I'm editing on a late 2010 MBP bought in July with 2.8GHz, 8gig Ram 1067 bus speed.

Thanks all.

 

[Liam Hall]

Why not just render your timeline?

 

[Ben Brainerd]

The issue is most likely a combination of your odd frame size and your RT settings.

What are your RT video quality settings at?

 

[Bruce Allen]

Ahh, interesting - how do RT settings affect brightness?

I ask because I hit my head against these gamme issues for years with FCP, from version 1.5 to the current version. It just made no sense.

In the end I just gave up and went to Avid, which shows everything at consistent brightness no matter what realtime / quality setting / PC / Mac / version of Quicktime / Quicktime gamma prefs etc.

If someone could come out with some kind of definitive recipe / rulebook for achieving consistent gamma in FCP that would be great of course.

Only problem is then probably Apple would release a new version of FCP or Quicktime which "fixes" it and introduces a brightness change somewhere else under different situations.

Bruce Allen
www.boacinema.com

 

[Hrvoje Simic]

It doesn't have anything to do with frame size and RT.

Luma levels don't just change on the timeline, happens after render too.

It's not just the gamma.

 

[Dustin Cross]

Bruce,

Avid has problems with Gamma too. Lots of people having problems with MC5. If you AMA footage it looks correct if you import it is too dark. Dealing with this problem on an Alexa shoot right now.


Dusty

 

[Ben Brainerd]

Ahh, interesting - how do RT settings affect brightness?

To be honest, I don't have a clue. I just know it does. I've run into something similar a couple of times and fussing with the RT settings (mostly jacking up the video quality) seemed to help.

RT in FCP is rather opaque. It plays nice with a very limited number of resolutions and editing timebases. Feed it something different and all kinds of odd things happen. The fact that the OP *didn't* have issues when he dropped them into a 1080p timeline is what leads me to believe it's a RT issue.

Now, of course, there's all kinds of fun with FCP gamma besides RT. Shifts on rendering out of Color, weird system gamma... It got better with FCP7/OSX 10.6, but it didn't get *fixed*.