Many people shy away from doing the maths, but a very little arithmetic goes a long way – honestly!! It’s well worth taking the trouble to understand the effect that resolution has on file size. The tutorial contains the absolute minimum of arithmetic you need to get the best out of your scanner and printer. Scanning from a print
Why scan from a print? The disadvantage is that some of the information in the original negative or slide has already been lost at the printing process. But sometimes the negative or slide is not available – such as when you want to carry out restoration work on an old photograph – in this case scanning from a print is the only option.
A flatbed scanner typically has an advertised resolution of “600 x 1200” or “1200 x 2400” or “2400 x4800” pixels per inch. In each case use the lower of the two figures when selecting the scanning resolution in the TWAIN dialogue box. The lower figure is the “optical resolution” of your scanner. (The scanner specification will probably quote up to something like 9600 ppi or more interpolated resolution.
Interpolation is a mathematical process where the extra pixels are estimated from the values of surrounding pixels. This has the effect of slightly degrading the image and does not give any real improvement. If you do have to interpolate, use Photoshop, which will probably make a better job of it.)