Scanning color photo quality question

I am scanning some 3-1/2x5 color photos to be enlarged into 4x6 later. Should I scan them at 300dpi or would a larger setting such as 350 or 400 produce a better enlargement. I realize the size increase is not that large, but I am also wondering if I make any adjustment to the image, like change brightness or sharpness, would the increase in dpi give some advantage since I read that any mods to a jpeg file degrades it, each time you do make some change.


I can make TIFF files – am using an Epson V500. I understand your idea to make and keep a master TIFF file. Would I then modify the Master TIFF files and keep a 'secondary' TIFF folder of modified TIFF images? Since I need jpeg files to print photos, could you recommend a freeware program to convert TIFF to JPEG?

Also, the Epson scanner uses “DPI” in the Destination/Resolution section. I read that DPI and PPI are used interchangeably and that is not correct. But for my purposes with the V500 scanner, can I consider them the same? And what dpi or ppi setting would be best considering that settings in the 1000's can take forever to scan? Some happy medium.

One last question: since the aspect ratio of 3-1/2x5 and 4/6 is a little different, when the enlargement is made, would the 3-1/2x5 get automatically cropped to some extent to fit the 4x6? If yes, then should I crop to 4x6 myself so I crop what I want to and not let the printer's machine do it arbitrarily?