Scan Line Art At The Resolution You Need
If you're scanning black-and-white line art for reproduction in print, here are two quick tips that'll help you get better results:
1. Scan the line art image at the dpi you'll be printing it. This is the one time we break our long-standing "don't-scan-at-too-high-a-resolution" ruleâ”but only when it comes to line art. If you're going to output your line art on a 600-dpi laser printer, scan it at 600 dpi. If you're going to output it to high-resolution film negs, scan it at 1,200 dpi (that's about as high as you'll need to go).
2. Scan your line art images in Grayscale mode. If you do, then you can apply filters such as the Unsharp Mask to help clean and define the lines, and you can use Levels to brighten the white areas.
Note: If you scan in Bitmap mode, you won't be able to use these two important line art cleanup tips, because they're not supported in Bitmap mode.