The first thing I do is set up some controlled light(s) (usually studio strobes… Battery powered strobes are too unreliable and are only used when there is no alternative). Second we make sure the lights are not causing shiny spots, or leaving dark areas. Then we photograph a Macbeth color checker in the same exact light as the painting. I have a computer program which matches the colors (all the colors are read not just neutralizing the gray scale) on the color checker with known values for those colors and adjusts whatever the camera’s sensor “thinks” the colors are to what they “really” are. Then we get the exposure perfect. Alignment needs to be perfect. And then I make files for the client’s needs. Files for printing presses, or photographic printing are made with different color spaces than files for the internet. Ideally, we will know exactly where the files are to be used and have access to the proper ICC profiles which we can apply to the files to “lock” the colors. Each device, paper, and use has its own ICC profiles. Proofs are made and sent to the client for approval before we make finals.
Photographing Art 2