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Old July 19th, 2010, 04:13 AM   #1
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Black vs. Black Gamma

I almost feel ashamed to ask this (after having used my EX1 for over 2 years, and experimented with the most part of all possible PP settings) - but as Vincent Oliver puts it: He who asks is a fool for five minutes, but he who does not ask remains a fool forever - so here it goes:

The Black setting being obvious (and changing easily seen by eye and on the scopes), just what exactly the Black gamma setting does?

The manual is not very clear on this one. So far, when setting up my PPs for either crushing or extending blacks, I used Black - not Black gamma. Today I tried to grasp the idea behind the latter by watching the scopes in Vegas, but haven't found anything obvious.

Comments welcome.
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Old July 19th, 2010, 05:27 AM   #2
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Tweaks lower half of the gamma curve basically. Move roughly 25% gray level between 15 and 35, give or take.
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Old July 19th, 2010, 06:36 AM   #3
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Remember this thread, from ages ago ?

http://www.dvinfo.net/forum/sony-xdc...mma-noise.html

Paul.
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Old July 19th, 2010, 07:38 AM   #4
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Thanks guys - this only confirms what I see with my eyes and scopes:

- there is no consensus on whether Black or Black gamma should be used for "black stretch/compress" in the traditional meaning of this term

- no matter how it's supposed to differ from Black, the effect of Black Gamma is by far more subtle than that of Black.
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Old July 19th, 2010, 04:18 PM   #5
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Black changes the black pedestal level. If you have something just above black and then you reduce the black setting to -20 (for example) then the near black object will disappear altogether as it will be pulled below the zero volt level and thus get clipped off. If you use black gamma the near black object will become much darker but should not disappear altogether as the dark parts of the image get compressed as opposed to clipped.

Raising the Black level will prevent anything from reaching black as it will raise the overall black level up so that it becomes a shade of grey.

It's actually easiest to understand if you can look at it on a waveform monitor where you can see the changes happening. Does your edit software have scopes?
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Old July 20th, 2010, 02:53 AM   #6
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Thanks for chiming in, Alister. Yes, I can confirm what you're saying with Vegas scopes.

The reason for my sudden "hesitation" has been that many people (on this forum and elsewhere) keep saying that "Black level" is basically the same as Black stretch/compress on other cameras.

In the actual fact, Black level should be understood as the "Pedestal" - while "Black gamma" is a closer equivalent of the traditional "black stretch/compress" control.
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