White point & Black point

F
Posted By
frankg
Oct 17, 2005
Views
205
Replies
1
Status
Closed
I’ve been asked for some stock images, and for them to be scanned with a White point of less than 252 and a Black point no less than 3. This keeps the rgb values slightly less than the full 256 range, and helps limit extreme values that will not print. And it helps limit errors when values fall outside the boundaries of an 8 bit file.
However, I have some files that are already scanned and saved as 16 bit. I do not want to have to go back and scan again, so how do I accomplish the same in PS?
Do I go to Levels and move the bottom Output Levels slider in at both ends by 3 points?
And if so, is this only true for files which have a Levels histogram showing that the values touch the end on one or both sides ? If they dont touch the end then they’re less than the maximum/extreme of 0 & 256 anyway – correct?

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Tom Nelson
Oct 18, 2005
In article <bAP4f.18702$>, frankg
wrote:

I’ve been asked for some stock images, and for them to be scanned with a White point of less than 252 and a Black point no less than 3.

However, I have some files that are already scanned and saved as 16 bit. I do not want to have to go back and scan again, so how do I accomplish the same in PS?
Do I go to Levels and move the bottom Output Levels slider in at both ends by 3 points?

That would work. You could make an action to do it.

And if so, is this only true for files which have a Levels histogram showing that the values touch the end on one or both sides ? If they dont touch the end then they’re less than the maximum/extreme of 0 & 256 anyway – correct?

Right. Those already meet their criterion.
Tom Nelson
Tom Nelson Photography

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