A blackish people is generally not considered beautiful as a fair one. Similarly an image having more no of lower intensity value or more blackish portion , is considered as a low quality image.
If these low intensity values are increased carefully then the resulting image may look fair one. So the main point is just increasing or adding intensity value good enough to suit the resulting image to our eyes.
Unfortunately this is not the case with human beings.
Have you seen the sketches ....??
what attracts you most in those sketch images...?
certainly its the line and its close and closer position that look different.
or simply the lines that are closest & separated both.
Some time you may feel that all this stuff are not straight forward but artistic too.