Is there a way in Photoshop to find the average luminance value of image?

[kkamin]

Is there some way to have PS calculate what the average gray scale value of the image is? For instance, if I were photographing a "normal" scene with a nice even distribution of tones, I would get a calculation value close to 128 on an 8-bit image (mid point of 256).

So essentially I want PS to average out the gray scale value of each pixel.

 

[Garbz]

Open the histogram window on the right hand toolbar, click the little down array and select "Expanded View" and also check "Show Statistics" Then select the luminosity channel, and read the Mean, Median and Std Deviation below it.

Just note that this is selection dependant so make sure you don't have a selection on the image while reading off the values.

/EDIT: Also note that this works on a luminosity function, and not red green blue values. I.e. An image entirely blue will come up MUCH darker than an image entirely green.

 

[kkamin]

Awesome, thanks!