Painters are not cameras. But if what you're striving for is realism, what is so different between an illustrator an a camera? This video discusses the painter's ability to manipulate reality for the sake of composition. The example shown in this video is a photograph, but it shows a step by step thought process that mirrors those I use while painting, and can be applied to any subject matter. Also, make sure to check out the Principles of Design videos - because they will help guide you in this process.