Colour Levels
August 10, 2005 12:07AM
Hello all...

I was asked the question recently but could not really provide a satisfactory answer so here I am.

FCP v4.5HD user wants to import a bunch of graphics from Photoshop. Now, some of them almost certainly possess "illegal" chroma levels. (ie; RGB levels greater than 235 and/or less than 16)

If a graphic does possess these "illegal" levels, does FCP clamp them (squeeze them into "legal" boundaries) or just pass them through unchanged? Does it also do the same with blacks that are too low and whites that are too high?

Best Regards,

Dave Forsyth
Re: Colour Levels
August 10, 2005 12:21AM
FCP doesn't automatically change the levels -- those will probably just look bad on a TV monitor. You'd have to use the Color Correction filters to change the settings. Use Range Check (Luma and Chroma) to see if your image is within legal broadcast limits.
Re: Colour Levels
August 10, 2005 03:38PM
Those are always the good reference for understand the video signal.

NTSC Video Measurements

PAL Video Measurements

Have Fun,
Antonio Hui

Re: Colour Levels
August 10, 2005 07:14PM
Hey Derek,

Thanks for taking the time out to reply...

I suspected what you said was true but here's the thing... I created a graphic in Photoshop with two rows of rectangles. In the top row, the rectangles were...

Red (R:255, G:0, B:0)
Green (R:0, G: 255, B:0)
Blue (R:0, G:0, B: 255)
Cyan (R:0, G: 255, B: 255)
Yellow (R:255, G:255, B:0)
White (R:255, G:255, B:255)
Black (R:0, G:0, B:0)

In the second row, the colours were the same but having different RGB levels...

Red (R:235, G:16, B:16)
Green (R:16, G: 235, B:16)
Blue (R:16, G:16, B: 235)
Cyan (R:16, G: 235, B: 235)
Yellow (R:235, G:235, B:16)
White (R:235, G:235, B:235)
Black (R:16, G:16, B:16)

If I use the Range Check (Both), the system tries to tell me that the Red, Blue, Yellow and Cyan rectangles are unsafe. Fair enough. That's the way I made them. But it also tells me that the Green, White and Black rectangles are OK. (?!?!) Furthermore, the supposedly "safe" Cyan and Yellow bars in the second row are also being identified as unsafe. At no time does FCP identify the blacks or whites as being out of range.

Now I have no difficulty with FCP not altering the saturation or luminance levels of a graphic file. I can deal with that. But I do have a problem with FCP not highlighting colours that I know full well are oversaturated and highlighting colours that I know are within the "legal" range.

Comments anyone?
Re: Colour Levels
August 10, 2005 07:27PM
FCP certainly alters luma levels to legalize them on import, but I'd use the broadcast safe tool / 3way-CC to ensure that the chroma is also safe.

[www.kenstone.net]

Should give you more info on how FCP handles luma levels.

Graeme



[www.nattress.com] - Plugins for FCP-X
Re: Colour Levels
August 10, 2005 11:21PM
Don't use Both. It's a pointless function, because you can't tell what it's showing. Use Luma or Sat. Range check does nothing for blacks. If you sequence is set to white, it flattens white to 100. If it's set to superwhite it will go up to 109.



All the best,

Tom
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