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Originally Posted by
GrumpyDiver
1. Resize to the final print size in whatever unit of measure you are looking at; in your example I would downsample to a 4 x 6 (inch?) print and sharpen at 100% after resizing. As I use an Epson photo printer, I set my dpi to 360; but HP and Canon printers are 300 dpi, so that should do fine as a default.
2. As you don't know the colour space people are printing to convert the image to sRGB (which is also what most commercial printers use).
3. Output to jpeg. In Photoshop, I find a quality level of 10 (maximum is 12) is more than adequate for a small prints.