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mycatisretarded
Joined: 18 Jan 2008
Posts: 124
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| Posted: Sun Jul 12, 2009 11:30 pm Post subject: The crushing of the blacks |
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Could someone please explain the term "black crush"- (or whatever it is) so that a fourth grader could understand it. Then i'll have my daughter explain it to me. I was reading one thread about gamma correction which lead me to this question. I'm sure the answer is in one of the thousand or so FAQs or stickys, but I'm too lazy for all all that. thanks.
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Tim in Phoenix
Joined: 21 Oct 2006
Posts: 4409
Location: Phoenix
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| Posted: Sun Jul 12, 2009 11:40 pm Post subject: |
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Hello
This results from poor calibration of a source device or a display, where there is no distinguishing between 5 IRE and 0 IRE
White crush is when a display is overdriven and one cannot tell 95 IRE from 100 IRE. IREs are steps of signal intensity. Crush means that detail that should be visible in deeps grays or bright scenes is not being revealed to the viewer.
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Last edited by Tim in Phoenix on Sun Jul 12, 2009 11:44 pm; edited 1 time in total
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garyfritz
Joined: 08 Apr 2006
Posts: 12088
Location: Fort Collins, CO
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| Posted: Sun Jul 12, 2009 11:41 pm Post subject: |
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Everything dark -- shadows, dim areas, black trenchcoats, whatever -- turns black. All those levels of gray get "crushed" to black. You lose all your shadow detail.
Raise the low end -- by raising brightness, or gamma boost, whatever -- and those levels of gray get boosted to "not black." Hopefully they get boosted to the correct levels. And hopefully you were able to avoid turning REAL black into dark gray in the process. That's the advantage of gamma boosters: they should boost the >0 levels without boosting the 0 (true black) levels or inappropriately boosting the higher levels. Cranking the brightness boosts the >0 levels but it boosts black too.
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Tom.W
Joined: 09 Mar 2006
Posts: 6635
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