I've taken photos before using point and shoot cameras and a DSLR Nikon (although in jpg, not raw format) and had them printed. They've all turned out well with rich colors. But now when I'm using a Canon EOS rebel t4i DSLR camera, shooting in raw format and processing the images as described in David's photo guide, they appear grayish when printed. They look fine to me on my Macbook Pro Screen before ordering the prints. What could be the cause?