it's probably different with every camera, but when i add borders to mine in photo shop, i also size them down. i think mine are probably 72 dpi and the longest dimension isn't longer than 11 in. it's really just a trial and error for me most of the time when i upload to deviant art. i just resize it till it fits on the screen. when you do resize them though, don't forget to keep a file of the original size in addition to the smaller one too so you can print them out large if you want to.