A black and white copy helps see the values; a color photo has better detail.  The order of difficulty in drawing from easiest to hardest is this:  1. other people’s drawings 2. black and white photos 3. color photos 4. real life. When using other people’s drawings, all the decisions about texture and value have been made. A black and white photo has all the value decisions right there for you. A color photo requires decisions about texture and value, but it is still a 2-dimensional image. Real life won’t hold still, doesn’t have any boundaries, is full color and changes each time you slouch a little lower!