This tutorial will show you how to get your photos sharpened with Lab color sharpening technique. The technique is really good if you want to avoid the color halos that appear when you add a lot of sharpening to a photo. By using this lab color sharpening, now you can apply more sharpening that you normally could get away with.
Step 1.) Open your photo and also get your Channels pallete ready.
Step 2.) Go to Image > Mode > Lab color to change lab color mode. You’ll now see that the channels have changed. There’s a Lightness channel with ‘a’ and ‘b’ channels which hold the color data.
Step 3.) Click on the Lightness channel, then go to Filter > Sharpen > Unsharp Mask. In this step you will apply an unsharp mask just to this black-and-white lightness channel, thereby avoiding the color halos. Your USM value is depending on how big your image is.
Step 4.) Now you can switch your image mode back to RGB color ( Image > Mode > RGB color )
See also: Photoshop Tutorials