Photoshop gradient creates an uneven histogram? Why?

kkamin

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When I create a gradient in PS, why are the ends of the histogram sloped upwards? Shouldn't it be an even distribution on tones and the histogram should be a black rectangle basically? Is it something to do with compensating for our visual perception?

gradient.png
 
Your gradient uses pure white and pure black....and everything in between, so your histogram reflects the two high points - left (pure black) and right (pure white).
 
Your gradient uses pure white and pure black....and everything in between, so your histogram reflects the two high points - left (pure black) and right (pure white).

Yup. and that histogram looks spot on to me
 
The photoshop gradient tool is actually not linear by default. Linear is boring and low contrast. Actually linear is also a bad word since in reality the displayed data on the screen actually has a gamma curve applied to it.

There's a setting in the gradient tool called "smoothness" which attempts to make a gradient appear to smoothly transition from one colour to another mathematical linearity be dammed. The histogram curves up and doesn't look perfectly flat because there is a small contrast increase to make the colours appear to transition more evenly. If you set the smoothness to 0% and re-do a gradient you'll end up with a lot more grey, less white and black, and also a perfectly flat histogram. (boring result though which is why histograms should not guide your photography but merely help analyse the result).
 

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