Photos can be a great time saver in the developing realistic paintings. However,they can present many problems:too much information,key stoning,black shadows,false colors,distortion of scale,and compositional problems. I can often tell when an artist is a slave to the photograph. One or more of the preceding problems will be evident, and the painter will say,"but this is how it looked".
One should think of the photo reference as a springboard to a painting that will eclipse it. Some solutions I use are: One shoot images with a 90 MM lens for scale.Take more than one shot with varied F stops for value variation. Simplify information (trace subject on parchment,next trace the tracing.Repeat until you have the essence).Check all vertical and horizontal lines against the edges of you paper to catch key stoning .Move or introduce objects to the best positions in the compositions. Finaly express yourself with unique colors,textures,edges,tones.etc.
One method I like is to paint an abstract under painting. Finish the work with complementary colors of the under painting. The marina painting above is an example.