Posted By:
Julie Vognarquality of the card. If it's crudely printed, you can scan it at 72 (or even 50) per inch, but enlarge the scan. That way you have a nice, tight picture, and the requisite size as well. A poorly-printed card will tend to go all tweedy, or appear to have evenly-spaced holes in the scan, if you do too many pixels per with it...
Don't use just ONE resolution, or size, for all your scans; all your cards and photos aren't alike, are they?