Smart Sharpening in Photoshop

The other preferred sharpening tool in Photoshop is Smart Sharpen. Like Unsharp Mask, Smart Sharpen offers Amount and Radius adjustments to control how much sharpening is applied. But Smart Sharpen takes a different, more sophisticated approach to controlling where the sharpening is applied and provides some interesting bells and whistles to boot. Smart Sharpen provides both tonal range and fade controls to specify where the sharpening is applied in an image. These two controls provide far more subtle control of sharpening than does Unsharp Mask.

The advantages of using Smart Sharpening are perhaps most apparent when sharpening images that have critical highlight and/or shadow values that you do not want to blow out or plug up by applying sharpening. Unlike the Threshold value that Unsharp Mask utilizes, which does not allow you to target the sharpening that is applied in a specific tonal range, Smart Sharpen allows you to modify the Sharpening in both the highlight and shadow areas without decreasing the sharpening amounts in other tonal areas. Here is a good example of where Smart Sharpen allows you to apply a significant amount of sharpening to an image filled with critical highlights:

1. Lets say you have the Winter Frosting. This image is packed with critical highlight areas. There are small specular areas that have no detail that add punch to the highlight. The danger is that if sharpened, the diffuse highlights with values in the 240s will be pushed into the specular area (250+) and lose critical detail. It is in this scenario where smart Sharpen really shines.
2. Zoom in on an area that contains several examples of diffuse highlights with RGB values in the low- to mid-240s (good diffuse highlight values that will show detail). 
3. Display the Info palette by choosing Window --> Info. Using your Color Sampler tool, place two color sampler points in the image that record these critical highlight values in the low- to mid-240s. You will see two color sampler points placed in the bottom of your Info palette. You will use these to monitor your critical highlight values as you apply sharpening.
4. Choose Filter --> Sharpen --> Smart Sharpen to activate the Smart Sharpen dialog box. The Smart Sharpen Basic mode dialog box appears. In addition to the familiar controls of Amount and Radius, there is also a Remove menu that can be used to mitigate specific types of blurs, such as Gaussian blur, lens blur, or motion blur, the latter of which allows you to specify an angle of motion. There is also a More Accurate check box, which is kind of misnamed. Typically you will want to leave this unchecked as checking it will apply sharpening to a greater portion of your image than you might intend, such as noisy pixels in your image; test this on your images, but normally leave this off and especially when sharpening noisy images.
5. Assign typical starting values of Amount = 100, Radius = 1.
6. Make sure the Preview option is enabled. Now view the RGB values of your color sampler points in the Info palette. You will see that with the application of 100% sharpening, these critical highlight values are now blown out in the 250s—not good!
7. To mitigate these blown-out critical highlight values while still applying the same amount of sharpening overall, click the Advanced button. Shadow and Highlight tabs appear.
8. Click the Highlight tab. Three value fields appear: Fade Amount (%), Tonal Width, and Radius. Assign the following values:

Setting Value Notes
Fade Amount 50% Start with 5 and work up in 5% increments while you watch the color sampler points on the Info palette.
Tonal Width 10% This controls the width in tonal range over which you will apply the Fade Amount. Because you want to fade only the highlights, you should assign a narrow value here.
Radius 1 Typically, you should set the same radius value here as you would in the sharpening field.
These values should lower the RGB values for the color sampler points back down into the more acceptable 240s range, while applying the full amount of sharpening to the remainder of the image.
9. After you set your initial values, you can fine-tune the relationship between Fade Amount and Tonal Width to achieve just the results you want. Higher Fade Amount values reduce the effect of the sharpening. Larger Tonal Width percentages apply the fading to larger tonal areas of the image. Note: This same type of sharpening can be applied to critical shadow areas as well, if the image composition demands it.