In lightroom, different sliders impact different pixel intensities. I'm looking for the exact values (or approximate ranges) of the various levels:
blacks: 0 - ?
shadows: ? - ?
midtones ? - ? (histogram calls this exposure)
highlights ? - ?
whites: ? - 255
I know that in default photoshop 0=black, 127=midtone point and 255=white. But the lightroom histogram sections everything into ranges.
From casual observation it would appear that each slider affects all values, however each slider affects each value to a different degree.
From slightly more detailed observation:
The Exposure slider affects the whole range with great effect
The Black and White sliders affect he entire range, with a larger effect as you move towards the end of the scale
The Shadows and Highlights sliders have the smallest effect, concentrating on the values closer to the ends, but still affecting the whole scale
Each slider appears to do a different thing:
The exposure slider shifts all values up or down
The Blacks and Whites sliders has a gradient of effect, the strongest being at the associated end, but not quite at the end
The Shadows and Highlights sliders have a gradient of shifting effect, with the strongest effect somewhere between the middle and the end, but significantly closer to the end.
Lightrooms' sliders are weighted distributions. It is not as simple as "Whites" are 127-255, "Blacks" are 0-127. The distributions are weighted, and different sets of sliders affect different ranges in different ways. Whites affects a broad range, but obviously affects brighter tones with more weight than darker tones. Same with blacks, only it's the inverse. Highlights and shadows are much tighter weightings, however they still affect a fairly broad range of tones.
Exposure is not midtones...it is the entire range of tones, highlights to blacks. Exposure is weighted, however, as the general idea with the exposure slider is to simulate what happens when you actually change exposure in the camera. It's just weighted less than the other sliders.
The tricky thing about these sliders is, as you move them around, more tones in the image fall into the ranges they affect, so there is a bit of a dynamic shift occurring as you move the sliders around. That's why shifting highlights to -35 may often do a lot, but shifting it to -75 does less, and shifting it to -100 does even less.
I would suggest you create an image with all 256 gray levels. Then you can move the sliders and see for yourself which values change. Your question of course assumes that these ranges are static and independent of the image in question, which might not be the case.
