How often have you heard the term “300 dpi” being tossed around loosely in the photography business like a bowl of salad? Your digital camera menu doesn’t have a DPI (dots per inch) setting so why should you concern yourself with this cryptic term at all? That’s right, you shouldn’t. DPI has absolutely nothing to do with digital photos but Capture Resolution does. Don’t believe? The Kodak digital printing guide has some useful info you may like to know but no more useful than the chart below. As a professional photographer of 8 years, I have often disassociated myself from matters in the business pertaining to printing — I leave that to the printing professionals so I can focus on what I love: the art of creating pictures with my camera.
Source: Photo Printing Guide
If you feel like dusting off the calculator, you can work out the print size of images with this formula:
[photo resolution] / 300 dpi = print size in inches (print lab typically prints at 300 dpi)
Example: a 1200 x 1800 resolution image will give you a high quality 4×6 print (4R print)
1200 / 300 = 4 inches and 1800 / 300 = 6 inches