It depends on more than just the display medium. It also depends on the kind of photo, how well the capture was exposed and focused, how your skills at processing it are, and what you expect to see in a print.
The Epson R-D1 is a 6 megapixel camera. ...
Two of my photos from the Olympus E-1 (5Mpixel) made outstanding prints sized to 20x26 inch image area that won recognition in two exhibitions. For printing purposes, I'd up-rezzed them to 20 Mpixel print files and printed them at about 200 ppi output resolution. For the viewing distance of a 20x26 inch print, that was more than sufficient to make them look great. 🙂
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