My human brain has a certain sensation of how “bright” a color is. More formally there is Lightness:
Human vision has a nonlinear perceptual response to brightness: a source having a luminance only 18% of a reference luminance appears about half as bright. The perceptual response to luminance is called Lightness. It is denoted L* and is defined by the CIE as a modified cube root of luminance:
Lab is one color model where colors with the same Lightness should appear to have the same “bright-ish-ness“. Except when i look at a color picker showing colors with the same L, they don’t appear equally “bright” to me:
Maybe it’s limited to my brain, and other’s don’t see it, but when i look at that color swatch some i see lines separating darker areas from lighter ones:
What accounts for this variation in Lightness?
- is it just me?
- is it because my monitor is not color calibrated with Photoshop’s sRGB?
- is it a limitation of a trisimululus color representation (i.e. red+green+blue) used by LCD monitors?
- is it a limitation of the Lab color model?
- is it a limitation of the XYZ color model?
Why is it that colors that should have the same Lightness have different apparent brightness?
Answer
Goes back to this illusion…..
The squares marked A and B are the exact same shade of gray.
Surrounding values alter the human perception. One reason why a neutral grey desktop is very beneficial when doing color critical work.
I don’t know all the science behind it. I expect it would take a medical degree to fully understand.
(photo from http://web.mit.edu/persci/people/adelson/checkershadow_illusion.html)
Attribution
Source : Link , Question Author : Ian Boyd , Answer Author : Ilmari Karonen
