I know that brightness is for adjusting the black level, and contrast, the white level. What is gamma? Is it the adjustment of the spread between the black level and the white level? Is it for adjusting the gray level? Or neither?

http://en.wikipedia.org/wiki/Gamma_correction
or more succinctly
http://www.digitalvideoessentials.com/glossary.php#G

It has an affect on the uniformity of the transition from black to white (gray level).

If 'Brightness' is for the adjustment of black level, why do some players also have a two-position 0 IRE/7.5 IRE black level switch?

If 'Brightness' is for the adjustment of black level, why do some players also have a two-position 0 IRE/7.5 IRE black level switch?

Those are two different things. One is setting 2% above black in relation to video black and the other is how video black corresponds to the output voltage.

NTSC standard is not at 0 IRE, that's like the extended levels you use for pcs (and not video). If you set it correctly for 7.5 IRE you allow for below black information. You also allow for above white information as well. Standard color space is not limiting, it actually allows for breathing room. And then whatever you call black, whether it be video black or absolute black, setting brightness is to ensure that whatever you call black is as black as can be without 2% above black being perceived as the same (that is to say that it's clipped).

Setting standard vs enhanced certainly effects the setting for brightness, but brightness has no effect on the other.

Those are two different things. One is setting 2% above black in relation to video black and the other is how video black corresponds to the output voltage.

NTSC standard is not at 0 IRE, that's like the extended levels you use for pcs (and not video). If you set it correctly for 7.5 IRE you allow for below black information. You also allow for above white information as well. Standard color space is not limiting, it actually allows for breathing room. And then whatever you call black, whether it be video black or absolute black, setting brightness is to ensure that whatever you call black is as black as can be without 2% above black being perceived as the same (that is to say that it's clipped).

Setting standard vs enhanced certainly effects the setting for brightness, but brightness has no effect on the other.

It's been a long time since we discussed IRE here and I think most of it was done in Chris Wiggles sticky at top. IIRC, IRE is analog only. 0 vs 7.5 is just a standard for reference black: US NTSC is 7.5, Japan 0. You can set either one as long as the display is adjusted to display "black" at the appropriate level. Setting 0 IRE does not prevent BTB from being displayed. IRE is basically voltage differences and can go negative. You can't equate IRE to 16-235 or 1-254 digital video levels.

larry

Oh I see, thanks you're right.

Yes, the whole PC thing and digital video really made a mess for some things. :) Factor that in with engineers that don't know anything about movies and studio levels and then there's the language/manual translation issues, ...

larry

What is gamma? Is it the adjustment of the spread between the black level and the white level? Is it for adjusting the gray level? Or neither?

Gamma controls the brightness/darkness of the midtones (ie grays) in the video image. It isn't too much more complicated than that.

It works pretty much exactly the same as the Gamma control in the display/graphics adapter properties on your PC. It's also similar* to adjusting the midpoint controls in Photoshop's Curves and Levels functions, if you've ever tinkered with those features when editing your own images. (*Those PS functions have a slight rolloff on the ends of their curves which makes them not true gamma controls though.)

If your player (or display) has a Gamma control on it, that should allow you to brighten or darken the picture, increasing or decreasing the perceived contrast in the image, without changing the black or white level. I emphasize "should" because sometimes in practice the black or white level may also drift up or down a bit as the Gamma is increased/decreased, requiring a slight readjustment to those other parameters. See remarks re the Gamma control on the Pioneer 410V player here as an example. [Luv that new table feature btw. Tks for adding that AVS!]