Posted by Roger Rouch on August 17, 2011 at 9:09 PM
Sorry if this remedial, but I've wondered about it more than once. When I open the RAW preview window with the collection of slider adjustments there is slider to adjust brightness and one to adjust exposure. When I move these two sliders back and forth they seem to affect the photo in a nearly identical manner. They must obviously have a different purpose, but I've yet to figure it out? Any help appreciated.
Posted by Richard Ditch on August 17, 2011 at 9:18 PM
It seems to me that the Exposure slider shifts the entire histogram, while the brightness slider is limited more to the central part of the histogram.
The Brightness slider works like the midtones slider in Photoshop's levels adjustment. I personally do not use this slider at all. I use the exposure, Fill and blacks sliders to correct most of my images.
Moving the “Exposure” slider to the right increases the overall brightness of an image, impacting brighter tones the most. Moving it to the left decreases the overall brightness while again impacting brighter tones first.
Adjusting the “Brightness” slider primarily effects mid-tones within an image. Moving it left will darken the overall image, with most of the effect being visible in mid-tone areas. Moving the “Brightness” slider to the right will lighten the overall image, with most of the effect visible in the mid-tones.
Posted by Paul DeCesare on August 18, 2011 at 1:16 AM
All three answers above are spot on. The technicals are that the exposure slider has algorithms to try and simulate the same effect as if you changed exposure at the time you took the shot. Brightness is intended to brighten or darken using tried and true algorithms that Adobe has invented and tweaked over the years to make it look as best as can be. That doesn't mean Brightness is super great, but just like Dodge and Burn, it has gotten better, but it's still not worth tweaking with. I align with Dennis, it's an untouched slider for me too. Maybe it'll improve in the future, but there are so many other ways I don't think it matters anymore.
The Exposure slider moves the white point, thereby expanding (or compressing) the histogram on the right end, mapping more (or less) tones into higher/brighter values. Brightness increases values in the midtones while preserving the white point where it is.
Guy is right. Exposure is used to set the white point and you can even see where it is just like with levels by holding the alt key while moving the exposure slider. You can then see where the brightest point of the image is and set it to white. Similarly the black slider sets the black point and again holding the alt key allows one to see the darkest point of the image. The brightness adjusts the tones between these two points. It is a very useful adjustment if you know what you're doing.
JR
Discussion
6 repliesSorry for the plug, but I cover these controls in detail in my Creative Processing Techniques eBook.
Guy
JR