Example: If your camera makes a 3000 pixel wide file, printing at 1200 dpi gives you a 2.5″ wide image (3000 divided by 1200 = 2.5). That would be printing at one camera pixel for each printer dot (1:1 ratio). But if you print at 1 camera pixel for 4 printer dots, you get a 10″ wide print. The formula is: (Camera Pixels) / (Physical Printer dot-per-inch) X (dot-to-pixel ratio) = (print size). So the previous example would be 3000 pixels / 1200dpi X 4 = 10″ wide print.

You’ll need to run the calculation for both the height and width. Canon and HP printers are usually 1200 dpi, while Epson is 1440 dpi. Offset printing uses 266 dpi.

Print this out and keep it with you. When you go on a shoot, look at the chart before you compose the shot and you’ll have an idea of how much you’ll need to crop before you shoot. This allows you to eliminate guesswork and get a much tighter shot.