Although all senses of the word contrast have to do with the word different, there are enough substantially different meanings that it is generally recommended that you just learn the sense (or senses) that currently interest you.
She increased the video’s contrast by making dark pixels darker and light pixels lighter.
Some technical definitions of contrast consider intensity of color. Other definitions consider only black and white.
We increased the photo’s contrast, so we can better see minor detail.
As beams of light tinted the clouds with blazing colors, everything gained a sharp contrast: brightly lit on one side, deeply shadowed on the other.
Christopher Paolini -- Eragon
The picture was beautiful, however, the composition perfect. ... In the last few months, though, it had started to look kind of eerie to me. Like I couldn’t just see the fine white-on-black contrast, or the way our features repeated themselves, in different measure but always similar, across our faces. Instead, when I studied it, I saw other things.