Resolution: Apples, Oranges & Hard Copy
640 x 480 = 300K File. Often poor quality. OK for TV. Poor for Print.
1280 x 960 = 1.3 Meg File Size, gives 5 x 7 Print limit.
1800 x 1200 = 2.2 Meg File Size, maybe 8 x 10 Print limit
Most cameras offer a Range of Image Sizes