Most images in Photoshop need sharpening when you reduce them, or importing from a scanner or digital camera. There are two ways (which generally provide the same results) that you may find useful.
- Change the image into Lab Mode and only sharpen the Luminosity Channel is one way.
- Another way is to choose Filter>Sharpen>Unsharp Mask, apply the settings that you want, then choose Edit>Fade Unsharp Mask, and alter the Blend Mode to Luminosity. The benefit of this method is that you can adjust the amount of the sharpening while you’re there instead of undoing and trying again.
There are, of course, other methods to accomplish the same thing, this is just an idea. If you have another way, please share it in the comments!