I wish to create a high resolution picture of two paintings, each in three parts for printing in a book, each across two pages that each measure around 12.5"x10". One painting is a triptych of three panels and another that is very wide (about 8 feet) and short (about 1 foot) street scene. I'm taking the photos with a Nikon D90 in RAW format at 2848x4288 pixels each using a Sigma 50mm f1.4 set to f5.6. I've taken the pictures outdoors in cloudy skies, moving the tripod sideways to be centered on each section being taken. When I go to stitch the photos together as three in a row, left to right, the colors and levels never quite match between the photos. I also get issues with more reflection on the left than the right, causing the abutted right of one to look more different than the abutted left of the next photo.
How can I use Photoshop CS6 to adjust one image to match the various light levels of another image so that they look the same when placed adjacent to each other? Perhaps I should instead leave the tripod unmoved and swivel the camera around tripod axis to shoot left and right of center and use perspective crop to correct for the distortion?