LAB Sharpening

In Adobe Photoshop, there are many different ways to do similar things and each way has its own strengths and weaknesses.  This can also be one of the features of Photoshop that tends to be the most initimidating.  As far as sharpening goes, there are countless different ways to help to sharpen your photos, and this article will show you a method that you may or may not have tried. 

Let’s try to demystify things somewhat and show you an easy and repeatable way to sharpen your images using the LAB mode.

It is important to note that this is a post-processing technique and does not have any effect on the “focus” of the photo, nor will it fix a blurry photo.  Sharpening a photo in post-processing simply enhances the contrast between light and dark areas, giving it the appearance of looking “sharper” or “crisper”.  I am going to tell you how to perform this technique in a simple, Kelby-esque way, leaving all of the techy explanations behind and just concentrating on how to make the picture look better, since that’s all that matters anyway.



After your open your image into Photoshop, and finish making all of your other adjustments, it will be time to sharpen your image.  I HIGHLY recommend always sharpening on a duplicate layer and not on the background layer, as this will allow you to make additional adjustments rather than being committed to whatever you had just done.


1.  Duplicate your background layer….  (keyboard shortcut Ctrl+J)

2.  Make sure LAYER 1 is selected in the layers palette. 

3.  At the top of the screen, click IMAGE >> MODE >> LAB COLOR.  (Choose DON’T FLATTEN if prompted.)

4.  Go back to the layers palette and click on the CHANNELS button.

5.  You will now see four channels:  Lab, Lightness, A, B.  Select the Lightness Channel.

6.  Your image will now turn to grayscale, as the lightness channel only holds the luminance information for your image.  It contains no color information.  The color information is stored in the A (green and magenta) and B (yellow and blue) channels.

7.  Go to the top of the screen and click FILTER >> SHARPEN >> UNSHARP MASK.

8.  For starting values, use AMOUNT = 100%, RADIUS = 2.5 pixels, THRESHOLD = 9 levels.  Amount is similar to a volume control dial, radius controls how far the sharpening bleeds out from an edge, and threshold controls how far apart/close together the pixels need to be before they are determined to have contrasting values.  For example, with a threshold of 0, every pixel in the image would be affected and at 255 no pixels would be affected.

9.  In the channels palette, click back on the lab channel and your image will return to full-color. 

10.  At the top of the screen, click IMAGE >> MODE >> RGB COLOR.  (Choose DON’T FLATTEN if prompted.)

11.  You should now have two layers, BACKGROUND and LAYER 1.  LAYER 1 is the sharpened layer and the BACKGROUND layer has been unaffected.  If the image appears too sharp, just lower the opacity of LAYER 1 until it looks suitable.  Because you have two layers, you can even now create a layer mask and paint in and out of the mask to control where you want the sharpening to lie.  Once you are finally happy, flatten the layers (LAYER >> FLATTER, or Alt+L+F).

12.  DONE!



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