The Photoshop CS2 Book for Digital Photographers Lab Color Sharpening This sharpening technique is probably the most popular technique with profes- sional photographers because it helps to avoid the color halos that appear when you add a lot of sharpening to a photo. And because it avoids those halos, it allows you to apply more sharpening than you normally could get away with. Step One: Open the RGB photo you want to sharpen using Lab sharpening. Go to the Channels palette (found under the Window menu), and you can see that your RGB photo is made up of