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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

Gamma in QuickTime -- again...

C

Chris Pickle

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Ok I know this issues has been discussed before, and I did a big search, but I couldn't find and answer.

I have Red footage down-converted to AppleProRes 720p. I'm previewing clips in QT and pulling pics here and there. The pics come out darker than the QT file. (and maybe a slight colour shift / wash, but it could be just the darker)

I thought I read about a solution way back. Any ideas?

Edit: A bit more info. When I open the pics in previewer, they are dark. When I open the pics in QT, they match the .mov file. Must mean that QT is using a specific gamma to view regardless of the file... humm, but which is correct to the actual prores file? The way QT is playing them, or is QT making them "brighter"?

Another note: Safari shows the jpg as matching the QT mov file in brightness.

Thanks,
Chris

ps - I'll try to attach the pic to see if it looks correct here...

can't seem to upload the pic.. will try again
 
JD Marlow said:
http://reduser.net/forum/showthread.php?t=23625&page=6
Click to expand...

Yes, I found that thread, but it's a bit greek to me. At least to my current issue. If I were to read it correctly, I'd say everything is f**ked, since Kaku even throws up his hands in his last post and he seems like an incredibly smart fellow.

I'd upload a pic, but I'll be damned if I can figure out how to get the pic up there. When I hit upload in the Manage Attachments pop-up window, it just sits there saying "Uploading files(s) - Please Wait" for ever. I let it cook for an hour last night but nothing...

Chris
 
KnockOutFilms said:
Ok I know this issues has been discussed before, and I did a big search, but I couldn't find and answer.

...
Edit: A bit more info. When I open the pics in previewer, they are dark. When I open the pics in QT, they match the .mov file. Must mean that QT is using a specific gamma to view regardless of the file... humm, but which is correct to the actual prores file? The way QT is playing them, or is QT making them "brighter"?

Another note: Safari shows the jpg as matching the QT mov file in brightness.

Thanks,
Chris

ps - I'll try to attach the pic to see if it looks correct here...

can't seem to upload the pic.. will try again
Click to expand...
Welcome to the confusing world of QT and gamma. Apple did provide an atom (field) in the video descriptor of QuickTime that allows you to note the gamma of the material. After you set it, it seems that various applications then ignore it and use their own assumed values.:angry2: It is not as easy as "FPC assumes 1.8", it seems to decide on the gamma based on the type of pixel it requests, and whether it is for scrubbing or preview playing.:angry03:
I would not trust any 8-bit image. Desktop Cinema on FCP is either a high bit depth image when stopped, or 8 bit yuv (on the default card) when playing.
 
I believe I'm still correct in assuming that we're all waiting for an update to Mac OS X that will provide a display of Gamma at the correct value of 2.2 (to match Rec 709). Until then, it's quite difficult to get an accurate sense of your image just on your display in the system, depending on where you are working.
 
Thanks for all the input. I'd heard of the issue, but I'm still a bit stunned that it hasn't been resolved.

I messed with my photoshop to get matching Gamma to QT / FCP, but when I send pics to the producer, he wonders why everything is a bit dark.

On a sort of side note -- how the hell does one upload a picture to a thread? I'd love to share some from a feature film we just completed.

Cheers,
Chris
 
Tico said:
Yes, but I wouldn't bet on it, JD.

:sad:
Click to expand...

Yeah, because even after they make the display gamma at 2.2, what happens when you need to work with gamma 2.6, the DCI format.

At least Apple corrects the gamma to 2.2 which is based on usual video monitoring gamma level, the compensation will be less.

I'm looking forward to figure out the ability of Gamma & Density's 3CP to sort this out at this point.
 
By the way Chris, as Craig explained, I guess Apple kind of cheat us in their handling the clips at still and playing back in motion, deeper depth at still and 8-bit YUV in motion.
I guess that is because to achieve realtime playback on rather wider range of computer with different performances.

Your 720 prores out from FCP gets 1.8 gamma so when you take it to Windows which is 2.2 gamma level, it looks darker. Someone on the net figured out by adjusting the gamma level in FCP at 0.9 or so would compensate it, but I'm not sure if that keeps an accurate gamma curve.

I think you are supposed to be able to just edit in FCP, even do some color correction with the plug-in, then send the timeline to Color and the color correction with the plug-in applies as the primary room, then use the FCP LUT in Color to adjust the gamma level.

I believe Evangelo has already figure out the consistent workflow and you can pay him to sort out your environment which includes consistency toward film out.
 
BTW, Kaku, thanks so much for taking the time and effort to help shed some valuable light over matters related to color rendition and workflow. To me, your contributions to this forum have been very helpful.

BTW... I had been running some tests on Snow Leopard 10A222 until last week, but had to stop to take care of other stuff before I got a chance to do any video-related tests.

Those will have to wait for now.
 
Tico,

Thank YOU for sharing your thoughts, too. I quit doing beta testing Apple because I got so busy, so counting on you for the report (? disclosure? haha).
 
I've have never and will never fault on a gov't security clearance, or corporate NDA in my life. And certainly won't in the future, either. But I do get your point.

:innocent:
 
Wait a minute, that didn't come out right I think. Sorry for my English. Just don't get caught! :). send us PMs.
 
I bought this product: video purifier
It's from the same guys of Bitvice. It's intended to clean the footage from noise of different kind. But It has two very interesting extra features:
1 very good scaling function
2 Gamma adjustment with the options to force the gamma atom in the output files!
I'm finding some compression problems but I think it's because the final output is proresHQ. I think you need to stay uncompressed for better results.
Please check it and tell me what you think. You can download the demo.
 
Luca,

I downloaded it and gave a quick try. Nice quick solution. I wish this could be done in Compressor but we can think as mastering dynamic processor in the audio world. Thanks for sharing.
 
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