Photoshop Tutorial Series

Color Correcting  |  Dodge & Burn  |  Sharpen

How to Sharpen an image in Photoshop by using Lab Color

The images that directly come from cameras are usually soft and dull, as the following example.  You definitely want to add some crispness and vividness, and Sharpen is definitely in your must-do list.  To share your photos with others, you would like to post them online, and usually the original size is too large to post, so the step 0 is to resize your photo to a proper size, say 640 * 480.  All the following steps are done in Photoshop CS2.

step 1: change mode from RGB Color to LAB Color.  Why?  I will explain it later.

Step 2: choose the Lightness channel.

Step 3: use the Smart Sharpen filter.  Someone would simply choose Sharpen, and others may use Unsharp Mask.  It is personal preference, and I like the new Smart Sharpen filter.

Step 4: choose proper parameters.  A typical combination is shown as followed: Amount 100, Radius 1.0.  To increase the sharpening effect, you would increase the Amount to 125 or even 150. 

If you prefer USM, here are some common parameter combinations recommended by Scott Kelby in his book "The Photoshop CS2® Book for Digital Photographers":

Soft Subjects: Amount 150%, Radius 1, Threshold 10
Portraits: Amount 75%, Radius 2, Threshold 3
Moderate: Amount 225%, Radius 0.5, Threshold 0
Maximum: Amount 65%, Radius 4, Threshold 3.  only when 1) visibly out of focus 2) lots of well-defined edges
All-Purpose: Amount 85%, Radius 1, Threshold 4
Web: Amount 400%, Radius 0.3, Threshold 0.  for Web graphics that look blurry

Step 5: change back to RGB Color mode.  otherwise you cannot save the image as JPG format.

Finally, view and save.  Here is the comparison between original image and the one after Lab Color Sharpening.

and compare the sharpened image with the one simply using Smart Sharpen filter in RGB mode

Look at the color difference between those 2 images, which one do you like?  Usually, Lab Color Sharpening could avoid the color halos that appear when you add too much sharpening to a photo, and it also reduces the color loss in sharpening.

References:

a Chinese version of Lab Sharpening: http://forum.xitek.com/showthread.php?threadid=304764
"The Photoshop CS2® Book for Digital Photographers" by Scott Kelby

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