Anne Kowalski

Monday, July 23, 2007

Quick Photo Sharpening using Photoshop CS3

One of the more common problems when working with digital photos or scans is making them realistically sharper. Typically, using the built-in sharpen tool produces results that are either not effective enough, or too harsh and overpixelated.

Here is our original photo, which looks a bit fuzzy:

The final goal is to sharpen it without creating overpixelation or artifacts.

First, create a smart object from the current photo. Simply right click the photo layer, then select “Convert to Smart Object”.

Converting to a Smart Object protects the layer in that it separates the filters applied, rather than lumping them together. The filters applied can be turned on and off as necessary, while the original layer is preserved.

In this case I want to sharpen only the rabbits while leaving the background as-is. I like using the Quick Selection tool whenever possible, since it is much quicker than using the Magnetic Lasso tool.

Here I have the rabbits selected. I’m not going to get too picky about the edges.

I then select Layer > New… > Layer Via Copy. The shortcut key Ctrl+J also works. This creates a mask so only the rabbits will be sharpened. I make sure I converted this new layer to a Smart Object as well.

Next, select the High Pass filter. It is under Filters > Other > High Pass:

A brief overview of the High Pass filter from Photoshop’s Help:

High Pass

Retains edge details in the specified radius where sharp color transitions occur and suppresses the rest of the image. (A radius of 0.1 pixel keeps only edge pixels.) The filter removes low-frequency detail from an image and has an effect opposite to that of the Gaussian Blur filter.

That’s why High Pass is a better option than the built-in Sharpen tool in many cases. The Sharpen tool sharpens the entire image, while the High Pass isolates only the edges.

You’ll see the photo with an ugly gray cast, but for now we need it to look that way so we can examine edges and detail. Play with the slider until you get a good outline that isn’t too thick. The thicker the outline, the more pronounced the edges will be. If your photo just needs a little tweak, then you will need only a small radius. A fuzzier photo may require a much larger radius. For my photo, I’ve selected a radius of 2.7 pixels, which gives a relatively minor tweak.

Once you are satisfied with the radius, then double-click the right side of the High Pass layer (shown circled in the photo in red.

From the Blending Options box that pops up, select Soft Light from the Mode drop-down box. Selecting any of the lights will get rid of that ugly gray overlay, but will sharpen to different degrees. I’ve found that Soft Light gives the most natural appearance, whereas the Hard Light mode is too harsh.