I noticed the other day at a happy hour where i was not having much fun, that if you smear finger oil around an iPhone screen with a white background, you can subtly manipulate how much the red green and blue pixels are magnified. I propose that something like hardening vegetable oil could be used (by someone who is a better artist than me) to paint subtle portraits using this method.-- JesusHChrist, Jun 17 2014random, halfbakery