
Remember: while you can always decrease resolution using editing software, you can never increase it.
A rough rule of thumb is that the memory required per picture is one half of the megapixel rating of the camera. Thus a 4 megapixel camera will require 2 Mbytes of storage per picture.
Professionals put the resolution required for parity with film at about 
This rule is somewhat subjective. Most find that 8x10s are satisfactorily produced with 4, 3 or even 2 megapixel cameras, although most notice some degradation and tiling at 2 megapixels and below.
In the following example, I have reproduced several images on the page in resolutions that represent the resolution produced by cameras printing an 8x10” print in 6, 4, 2 and 1 megapixel resolution.
300 pixels per inch, same as a 6 megapixel camera printing  | 225 pixels per inch, same as a 4 megapixel camera  | 
an 8x10  | printing an 8x10  | 
160 pixels per inch, same as a 2 megapixel camera printing  | 100 pixels per inch, same as a 1 megapixel camera  | 
an 8x10  | printing an 8x10  | 
5