Gamma shift with P2 to FCP vs. P2 to Avid Express Pro

The issue being discussed here isn't whether the monitor displays the image accurately but rather, why two images side by side, on the same monitor look different. The quality of the moinitor is moot, its clear that the two pictures can be compared equally and its clear that there is a big difference. The question is, why has the image changed. But which is the actual image recorded by the camera? Can we be sure that the P2 viewer footage is un-enhanced?

I've experienced this recently myself I think.
 
You should be able to use bars and the scope of your NLE to examine the colors and see which is correct.

If all else fails, create an image with known properties in Photoshop, and see how the editor handles it. If the still displays correctly, render it out as a video using uncompressed RGB and/or the DVCProHD codec, and open that. Is it still accurate?
 
I did Barry's test of exporting Color bars from FCP to the camera and then back from the P2 to FCP and there wasn't much difference. The RGB values were off by one or two points in red, blue, and teal, but still close.

I also did this test changing between 0% black and 7.5% black in camera, and it was the 0% black in camera that actually had the off values.

I honestly can't say what it is outside of annoying. And I didn't have time to move over to the Avid bay to see what the footage looked like, so soon enough.

The P2 viewer footage looked pretty much like what I saw on set between the LCD and External Monitor. So I was surprised when I saw the contrasty darker image in Final Cut.
 
"I did Barry's test of exporting Color bars from FCP to the camera and then back from the P2 to FCP and there wasn't much difference. The RGB values were off by one or two points in red, blue, and teal, but still close.

I also did this test changing between 0% black and 7.5% black in camera, and it was the 0% black in camera that actually had the off values."



I don't quite know what you mean about the black levels- what was off?
On the color bars was the pluge in the same place?
 
When recording the color bars to p2, then re-importing into Final Cut Pro, the RGB was innacurate between the original FCP generated bars and the p2 imported bars.

BAH! I'll solve my issues and just move to Avid. -grumble-
 
So, using both YUV and RGB render settings, I exported my sample shot from FCP using the DVCPRO HD codec and then imported it into Avid Express Pro using both the RGB and the 709 import settings. The result, once in Avid, was that each shot, whether YUV or RGB render setting exported, or RGB or 709 imported, looked exactly the same as my original MXF files in the Avid. The annoying extra contrast and vertical banding had disappeared.

I then, using the Avid's RGB and 709 export settings, exported my sample shot from Avid using the DVCPRO HD codec and imported it into FCP (unlike Avid, FCP gives no import options regarding color space). The result, once in FCP, was that neither the RGB or 709 shot looked like the sample shot in FCP. The RGB Avid shot looked slightly less contrasty than the FCP shot, but it also had some of that vertical banding you can see in the JPEGS I posted. The 709 Avid shot had a little of the vertical banding, but otherwise looked exactly like the original MXF shot in the Avid.

<<for those unfamiliar with the Avid, it allows you to change the color settings on import or export – RGB or 709. According to Avid, ITU-R 709 color space is the international standard for HD with black at 16 and white at 235 – I think this is similar to FCP’s YUV render setting.>>

My other test was to uprez each sample shot to full, uncompressed 1920x1080 HD for use in Adobe After Effects.
<<In case you’re wondering why I do this, I’ve found that the only way to get footage in and out of After Effects without gamma or color shifts is to go out at pure, uncompressed from my NLE (whether Avid or FCP). I do my work in After Effects and then export a similar uncompressed file. I then reimport this into what my originating NLE was and cut into the DVCPRO HD timeline.>>
When in After Effects, each sample shot looked exactly as it had in it’s respective NLE. The FCP shot looked contrasty and dark with vertical banding, and the Avid shot looked better exposed with no vertical banding.

So, what can be concluded from all of this? I’d like to know everyone’s opinions, but for me, it seems both FCP and the Avid make their quicktimes a little differently when dealing with the DVCPRO HD codec.

It seems that whether you do your “offline” edit in FCP or Avid Express Pro, you can take your quicktime or MXF files to a high end Avid Nitris System for color correction and output to HD tape, and you’ll have identical results.

Now, I’m guessing that if you take your “offline” Avid Express Pro sequence to a tricked out FCP for color correction and output to HD tape, you’ll have to do a little bit of gamma adjusting.

Unfortunately, I don’t have a professional HD monitor on my home computer, but, my test with After Effects proves that the two editing systems certainly interpret and affect the same footage in different ways. ((It is clearly not just a matter of monitoring when FCP and Avid quicktimes don’t match each other in the same third party application.)) I think you could end up in trouble if you took your DVCPRO HD quicktime through a multitude of programs, i.e. Avid, to After Effect, to Shake, to Motion, back to Avid. It’s kind of a squirly codec in many ways.

Anyways, I'd love to hear people's thoughts regarding this.


p.s. I know this could be the topic of a whole new thread, but in my testing I discovered that FCP quicktimes are a frame off from Avid’s MXF files.
 
Here's some relevant info from Apple:

http://www.apple.com/support/shake/lbn/40/#Gamma

It includes this excerpt:

"Final Cut Pro assumes that QuickTime movies for codecs that support the YUV color space (including DV, DVCPRO 50, and the 8- and 10-bit Uncompressed 4:2:2 codecs) are created with a gamma of 2.2. This is generally true of movies captured from both NTSC and PAL sources. When you eventually output the sequence to video, or render it as a QuickTime movie, the gamma of the output is identical to that of the original, unless you've added color correction filters of your own.

However, during playback on your computer's monitor, Final Cut Pro automatically lowers the gamma of a sequence playing in the Canvas to 1.8 for display purposes. This is to approximate the way it will look when displayed on a broadcast monitor. This onscreen compensation does not change the actual gamma of the clips in your sequence."

Interesting I think, but unfortunately, it still doesn't explain the differences others have found when exporting raw material to other apps.
 
Ted Spencer said:
Here's some relevant info from Apple:

http://www.apple.com/support/shake/lbn/40/#Gamma

It includes this excerpt:

"Final Cut Pro assumes that QuickTime movies for codecs that support the YUV color space (including DV, DVCPRO 50, and the 8- and 10-bit Uncompressed 4:2:2 codecs) are created with a gamma of 2.2. This is generally true of movies captured from both NTSC and PAL sources. When you eventually output the sequence to video, or render it as a QuickTime movie, the gamma of the output is identical to that of the original, unless you've added color correction filters of your own.

However, during playback on your computer's monitor, Final Cut Pro automatically lowers the gamma of a sequence playing in the Canvas to 1.8 for display purposes. This is to approximate the way it will look when displayed on a broadcast monitor. This onscreen compensation does not change the actual gamma of the clips in your sequence."
Click to expand...

That's interesting. But when I output, it's still just the same as within the timeline.

And Jim, thanks for the tests between Avid and FCP. I have a question for ya since you're more active in Avid than myself: When you adjust the gamma of your clip within FCP, does it expose more "noise" than the file originating in your Avid clip?

I'm speaking in terms of matching the two images as close as possible. At full-frame do you see more artifacting going on in the gamma-corrected versus the file that originated in Avid?
 
Kholi said:
When you adjust the gamma of your clip within FCP, does it expose more "noise" than the file originating in your Avid clip?

I'm speaking in terms of matching the two images as close as possible. At full-frame do you see more artifacting going on in the gamma-corrected versus the file that originated in Avid?
Click to expand...

That was going to be the next thing I was going to try. I won't have time to do anything until tonight, but I'll let you know.
 
Kholi said:
When you adjust the gamma of your clip within FCP, does it expose more "noise" than the file originating in your Avid clip?

I'm speaking in terms of matching the two images as close as possible. At full-frame do you see more artifacting going on in the gamma-corrected versus the file that originated in Avid?
Click to expand...

Hey Kholi,

So, when I lowered the Gamma and Chroma levels in FCP, I was able to make the shots match fairly closely with what I had in the Avid Express Pro. I didn't seem to pick up any extra artifacting or grain.

I'd be interested to see the results of a test where FCP, Avid, After Effects, and Shake were all hooked up to the same HD Monitor with a waveform.
 
Thanks for the test Jim. I suppose of it really is a matter of correcting the gamma to match then it's fine. I just dislike that it's like that in the first place.

I'll be going from FCP to After Effects and possibly Shake meself soon. Just wanted the best source material for each move
 
I took a quick look at this issue on my Powerbook (1.67 GHz, last version), and can confirm that there is indeed a big difference in the look of a clip in the P2 import window vs the viewer or canvas windows in FCP (5.1.2). Much darker in FCP just as others have reported. Changing the Gamma preference from "accurate" to "approximate" helped quite a bit, but there is still a noticeable difference. Apple needs to take a serious look at this...
 
What do y'all have FCP's gamma set to in the User Preferences? Or are you not bothering to check that?
 
Can you elaborate Ben? the only gamma setting I see for user prefs relates to imported stills, Is there another or is this the one to check?
 
What gamma setting, BenB? I didn't know there was one.

However, I got to a calibrated editing monitor out of FCP and my footage was about the same that was in the p2 viewer as I suspected. So the timeline is wicked weird.
 
So the shift DOES seem to be related to how FCP deals with monitor color profiles. A pro monitor will be setup with it's own color profile which would explain why the shift doesn't occur on one and the reason why the footage seems OK when taken from FCP into AVID which applies it's own color profile, if I'm understanding correctly.

I would suspect the reason you're seeing similar results on exported footage would be because FCP is applying it's color profile to the exported footage. Is there a way to force a different color profile within FCP?
 
Something just doesn't seem right to me about this. Its not something I have been aware of previously, perhaps its because I used to use P2 log for importing so I never saw the raw files and the timeline side by side but I have definately noticed that my footage looks too dark on my last couple of shoots.

Is this another little change coming from the crossgrade to 5.1.4?
 
The color profile thing was new to me. That would be up for BenB to tell us since he seems to have more experience.
 
BenB is likely talking about the setting under...

FINAL CUT PRO MENU > SYSTEM SETTINGS > PLAYBACK TAB > GAMMA CONTROL > ACCURATE/APPROX

obviously, "accurate" is the ideal setting. but takes away a bit of the system's real-time capability.
 
forgive me if someone posted this... from the Final Cut Pro user guide..

What Is Gamma Correction?
Gamma correction is necessary for proper color and brightness rendition of video during playback. Gamma correction compensates for the fact that video display devices (such as televisions) inherently alter the middle tones of an image in a nonlinear fashion. For example, televisions inherently reduce the brightness of the video signal in a predictable way, resulting in images whose midtones are darker than expected. To compensate for this darkening on the television, camcorders record images using an opposing brightness curve. However, when the video from your camcorder is shown on your computer display, you often see the image brighter than expected, because
the image was intended for playback on a video monitor. Gamma correction must be applied to the video so it appears as intended.
Click to expand...
 
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