What size digital file or transparency is best?
Always, the bigger, the better. You need either a high dpi or a large image size for the best results. If you have both you will get a better print. DPI should be 200 to 300+ for best results. Lower DPI may work fine if you have a large image size and a small image size may work if you have a high DPI. The larger we are printing the more important file size, DPI and quality is!