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Old November 7th, 2006, 01:47 PM   #1
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"Crunched Black Levels"

can someone tell me in plain english what "crunched black levels" mean.

i had a video engineer tell me my video had crunched black levels and i would like to know what that means and how i could fix this issue within premiere pro 2.0.

thanks

joel
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Old November 7th, 2006, 01:56 PM   #2
 
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fundamentally, it means you're clipping the shadows. In analog terms, your minimum IRE settings are near or below zero. Check your footage in a waveform analyzer to see where this is happening in your footage.
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Old November 7th, 2006, 05:34 PM   #3
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Or, in plainer english ... parts of your image that should be dark but not-quite-completely-black are in fact completely black.

So any detail in those areas, for example in your shadowed areas, has been lost ....
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Old November 7th, 2006, 05:49 PM   #4
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Ok thanks,

so i need some advice.....

I know where I went wrong. I had a couple of shots in low light of subjects with dark colored skin, so I changed the (RGB)white input levels from 255 to 220 or so and then the (RGB)Black input levels to around 10 or so. So if this crunches my blacks how can I make a scene brighter and add contrast and still not "crunch the blacks?" is it possible or is the footage lost...

Joel
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Old November 7th, 2006, 05:52 PM   #5
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Your mistake was setting the black level to 10. Use the Curves tool instead of Levels, and create a gentle slope.
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Old November 7th, 2006, 05:58 PM   #6
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Which "curves tool" are you referring to? I donít seem to find a tool named "curves" in Ppro 2.0.


Thanks,

Joel
Sorry if I seem clueless, i am really not, obviously coloring in not my forte.
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Old November 7th, 2006, 08:39 PM   #7
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If you look under /Video Effects/Color Correction/ you will see Luma Curve and RGB Curves as two of your options.

Levels is a subset of Curves. With Levels, you can adjust White, Black and Grey levels - this would be equivalent to using Curves with 3 points specified(one at each end of the line, and one somewhere in-between).

Curves lets you add additional points to achieve, say, an S-shaped curve.
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Old November 7th, 2006, 09:25 PM   #8
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ok thanks i'll try it.......
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Old November 8th, 2006, 02:58 PM   #9
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blacks

Joel,

With dark areas you can also play with the gamma to see more detail.

Thanks for posting your question, I learned a couple things reading the posts.
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Old November 8th, 2006, 03:07 PM   #10
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I believe (although I am happy to be corrected on this) that adjusting a single-parameter "Gamma" control - which some applications provide - is exactly equivalent to dragging the grey level slider in 'Levels', while leaving the white and black levels at 255 and 0 respectively.
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Old November 8th, 2006, 07:13 PM   #11
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well i tried the RGB curves tool and looks ok to me and on the waveform as well hope the station will ok it.....


joel
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Old November 9th, 2006, 08:15 AM   #12
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Correct, Graham. The gamma adjusts the midtones.
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