Sharp Images.
Why sharpen images you may say, but did you realise that all digital images are inherently unsharp and have to be sharpened at some stage during the process before printing – if you want to achieve optimum results.
Photoshop provides several ways to sharpen images – you’ll find several under Filter > Sharpen > Sharpen Edges > Sharpen More > Smart Sharpen and > Unsharp Mask!
If you are happy with your chosen method then you need read no further, but if you want to try one of the following means, they may provide you with better (more believable) results.
After opening an image and having completed your adjustments (Levels, Curves, Colour balance, size etc), flatten the image and go into Image > Mode > and then Lab Colour.
Take a look at the Channels tab and switch off everything except the Lightness channel.
Then go to Filter > Sharpen > Unsharp Mask and use the following settings as a first trial: Amount = 75%; Radius = 1 pixel; Threshold = 0. Click Ok. Now go back to Image > Mode > RGB, and save the image as normal.
These settings seem to work pretty well in most situations. (more)