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Gamma Shift?

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Alec Eagon
Gamma Shift?
on May 13, 2013 at 10:35:16 pm

Hey yall,

I've been experiencing what appears to be a significant gamma shift after exporting both a Self-Contained .Mov file (with NO export settings altered--aka just "as-is") and also a Compressor reference file from Compressor also "as-is" with no settings altering anything from the original footage.

I have been viewing the export tests via QT7 w/ "Enable FCP Color Compatibility" on.
I have also tried VLC and the same shift appears. I've dealt quite a bit with .h264 gamma shifts but never experienced a color/contrast shift like this when just exporting raw.



*This is how the footage appears in FCP6:




*And this is how it appears after the two export attempts (FCP & Compressor):



***

Any ideas what might be going on?

I imagine it is something small and silly I am forgetting in FCP...

Thanks a lot!
-Alec

Alec E.


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Shane Ross
Re: Gamma Shift?
on May 13, 2013 at 10:46:09 pm

The FCP canvas and Viewer aren't color accurate. Not designed to be color accurate. For accuracy, you view on an external HDTV or broadcast monitor via a capture card. If your ultimate destination is the web, and you need accuracy in your edit system...don't use FCP 7 or earlier. It isn't designed for this purpose.

FCX was designed with this in mind. I hear that Adobe CS6 does this too...although it doesn't offer a "same as source" export option...it always recompresses to a different format. But, it's more accurate than FCP.

Avid, like FCP, is not accurate.

Shane
Little Frog Post
Read my blog, Little Frog in High Def


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Alec Eagon
Re: Gamma Shift?
on May 13, 2013 at 11:18:33 pm

Huh...wow. Well that is sure something. Not quite sure how I have never known this.

So a calibrated Apple Cinema Display does me now good with FCP6 because the program itself was not designed to show you an accurate representation of the footage you are working with?...Is this correct? I mean, of course I believe you, but this also seems to be slightly absurd, like something they should have taken care of in the first version of FCP...but maybe I am just too green in the world of media production even with 7-8 years under my belt.

***

Gosh, forgive me, I am kind of embarrassed that I never knew this. I imagine this is sort of the missing piece in the overall explanation all lengths we've had to go to get accurate color representation in our previous 16mm>WebVid work flow (even after we've tended to the .h264 shifts with the best possible)?

The thing that I don't get though is that, considering that I am an accurate color-fidelity nut (or at least I thought), I do not recall ever experiencing this sort of shift when playing back unadulterated exports of color 16mm footage via compressor...when we have had that workflow, the place where everything got screwed up was in the h.264 gamma shift while converting to web video, but there was never any noticeable difference between how the footage in FCP and and full res exports via Compressor being played back in QT7...is it just 100x more noticeable because it is B&W this time?


***

So I guess this presents a new problem: We are in the final stages of editing a 25-30min short shot entirely on 16mm B&W. "The film" (insofar as we have sculpted it in FCP6) globally should have the darker/slightly underexposed look of the "FCP still" above...

Does anyone have any suggestions about how we might go about achieving the same contrast/black depth/color as what we are viewing in FCP6? Is it possible to trace the what is displaying the footage the way that it is in FCP?

...or would the only thing to do at this point be to: 1) take screenshots of each shot as we view it in FCP, 2) get accurate representation of the footage via external HDTV or FCPX, 3) have the film globally colored as close as possible to the aesthetic we've become accustomed to in FCP6?

***

Thanks a lot for waking me up here Shane. Though it's partially disappointing, this could be huge for our workflow in the future.

-Alec

Alec E.


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Shane Ross
Re: Gamma Shift?
on May 13, 2013 at 11:47:13 pm

[Alec Eagon] "So a calibrated Apple Cinema Display does me now good with FCP6 because the program itself was not designed to show you an accurate representation of the footage you are working with?...Is this correct?"

Correct. The Viewer and Canvas are there to show you what you are doing. To see what the footage looks like, you need a IO device and HDTV or broadcast monitor. It isn't like Photoshop and those calibration tools. Those are designed to show you that what you do in Photoshop is how it will appear on the computer, and in print. FCP...doesn't work that way.

This was one of the BIG selling points of FCX...that what you see in the display is 100% accurate with what you export from the app.

[Alec Eagon] " I do not recall ever experiencing this sort of shift when playing back unadulterated exports of color 16mm footage via compressor...when we have had that workflow, the place where everything got screwed up was in the h.264 gamma shift while converting to web video"

H.264 makes it more pronounced. It's a decent codec, but prone to gamma shifts. Which is why stock footage companies still compress to PHOTO JPEG.

[Alec Eagon] ".is it just 100x more noticeable because it is B&W this time?"

Perhaps...because you are more focus on the luminance and the chroma isn't getting in the way.

[Alec Eagon] "Does anyone have any suggestions about how we might go about achieving the same contrast/black depth/color as what we are viewing in FCP6?"

Get an external monitor (Good HDTV or broadcast monitor)...an IO device from Blackmagic design or AJA or Matrox. Correct there and know that's a true representation of what you are working with. And then when you compress for the web, know that there will be some shift as you are compressing the footage, thus losing some color information. Just like what happens when my TV shows are broadcast...they NEVER look the same way as they did on my broadcast monitor. Even if I watch the TV show on my same monitor. It's compressed for air...and that tweaks the color.

Shane
Little Frog Post
Read my blog, Little Frog in High Def


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Alec Eagon
Re: Gamma Shift?
on May 14, 2013 at 12:16:58 am

[Shane Ross] "Get an external monitor (Good HDTV or broadcast monitor).."

Do you have any recommendations for a "Good HDTV" and will I need to to calibrate this or will the AJA/BM/Matrox card + the HDTV be naturally producing an accurate general broadcast image?

The initial showings of this film will be HD digital projection, thus the telos right now would be to achieve as little color shift as possible FCP > Compressor > Apple Pro Res HQ file being played back via HD digital projector...

Would the setup you have recommended produce for us the most solid, least shifty, color workflow possible, FCP to HD projection?--or for that matter, to any broadcast device (obviously pending varying unchangeable characteristics of different devices)?

***Oh and is there a particular card you would recommend?
(my current graphics card is an "ATI Radeon HD 5770 1024 MB")


Thanks a ton Shane,
-Alec

Alec E.


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