prores to color contrast+sat shift please please help

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prores to color contrast+sat shift please please help

Hi,

I'm using my macbookpro monitor throughout this problem.

I have a sequence of shots in prores 422 format that look great in quicktime etc. I've imported them to final cut (7) where they look fine (same prores settings) and then sent them to color. In preferences color is set to render as same settings as the shots.

When i view the shots in color they are brighter and more saturated, when i render them out without a grade and watch in quicktime (7.6.4) they are brighter with more sat (ie the same as how they appeared in color). When i render the exact same original shots that i sent to color out of final cut (same prores settings throughout) and watch them in quicktime they are fine. Both are rendering out the same shots without any changes yet they look completely different. Color is really screwing up the shots. What is going on? This renders color useless to me and it's really frustrating me. I can't believe it. Thanks for any help or advice you can give.

macbook pro, Mac OS X (10.5.8)

Posted on Jan 12, 2010 5:22 PM

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Answer 1

kedbear Author

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Jan 13, 2010 3:06 AM in response to kedbear

just to add to this:

If i export a clip from final cut using 'export quicktime movie' and leave settings the same as the clip the contrast and saturation change

If i export the same clip in final cut and choose 'export using quicktime conversion' and set the settings the same as the clip (prores 422) then everything is fine.

If i import the good clip into color the same saturation and contrast shift is present. If i export this clip from color it is still present.

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Answer 2

JP Owens

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Jan 13, 2010 9:21 AM in response to kedbear

COLOR assumes that whatever you are grading (under Quicktime) is destined for CCIR709 (HDTV) colorspace and interprets the media to have a natural gamma coefficient of 2.2. Apple Snow Leopard was supposed to bridge the standards difference (1.8 in computer graphics) by switching everything to 2.2, but the implementation is not complete, and requires actions on the part of the operator. There are still some QT internal conflicts, even within the COLOR module (still store, for example) that are not fully resolved.

This is most likely the cause of your anguish.

jPo

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Answer 3

kedbear Author

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Jan 13, 2010 10:07 AM in response to JP Owens

thankyou very much for replying.

However, do you have an idea why when exporting from final cut using 'export quicktime movie' (using the same settings as original clip throughout) i get the same brightness and saturation shift as color, whereas i don't get these shifts when using 'export using quicktime conversion'? I have the exact same settings as the original clip in both instances but one screws up the image.

Do you know what i can do 'as the operator' to help my situation? I already have my monitor set to a custom 2.2 gamma since buying the macbook pro.

What concerns me about color is the original file i am importing is already graded for broadcast, but simply by importing that grade into color it is shifting the contrast and saturation, and then when exporting it is likewise shifted for good. This can't be right?

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Answer 4

JP Owens

Level 4

2,015 points

Jan 13, 2010 10:22 AM in response to kedbear

macbook pro?

The Quicktimes aren't tagged, so QT/Final Cut/COLOR are handling these files blind.
If there is a difference between Export using QT conversion and export QTmovie, then there is a systemic problem. I believe that Apple has completely dropped the ball in transition and unfortunately, there is very little we can do as operators, since now that we think we're operating in 2.2, but clearly a great deal of Quicktime pays no heed at all, we now have no idea what standard we're working to. Even when system Monitor preferences are "set", everyone is getting different behaviours.

Grading on a new glossy /LED MacBook Pro is not recommended. That's about all I can say about that. There is no way that a consistent calibration will hold with these devices.

jPo

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Answer 5

kedbear Author

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Jan 13, 2010 1:01 PM in response to JP Owens

I don't plan to grade on my macbook pro, was playing with color and just discovered this and wanted to know what was going on.

I still don't understand the colour shift and brightness shift that is happening and why in color. If color is calibrated to 2.2 and assumes what it is being fed is at 1.8 (why would it assume this?), why is my 2.2 clip being so messed up by it?

thanks again

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Answer 6

JP Owens

Level 4

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Jan 13, 2010 3:05 PM in response to kedbear

and assumes what it is being fed is at 1.8 (why would it assume this?)

Oh, but it doesn't. It assumes that 2.2 is coming in (because it is designed to work with 709 video I/O), but the display is still a bad match -- what COLOR does assume is the grade judgements are being made on an external SDI device.
However, within COLOR itself, there are discrepancies. The still store uses a system QT algorithm to generate the media and store it in the User Library -- but it does it on the wrong gamma setting. So then all your reference stills are wrong. You can see this instantly when creating the still and it comes back in a split with the original grade.

Its supposed to have been fixed in 1.5.1, but I'm not convinced that it has been properly addressed.

jPo

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Answer 7

kedbear Author

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Jan 13, 2010 4:40 PM in response to JP Owens

sorry yes, of course, mac is 1.8 and color assumes 2.2. Thing is, if it is being fed something that is already 2.2, it changes it further by making the 2.2 gamma adjustments to something that is already 2.2.

My monitor is already set to 2.2, and color assumes 2.2, so in theory it shouldn't change anything right?. I should only notice a difference if my display was set to 1.8. Either way, why is color changing the prores file i import when i render it out without a grade?

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Answer 8

JP Owens

Level 4

2,015 points

Jan 14, 2010 10:14 AM in response to kedbear

Either way, why is color changing the prores file i import when i render it out without a grade?

It shouldn't be changing it a great deal, but having put that...

There is a YCbCr -->RGB -->YCbCr conversion, so there will be a difference no matter what. The reason why you send media to COLOR is to change it to something else. If you don't want to, don't send it???? ;-P

jPo

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