- Thirteen. Sharpening Images
- #93. Using the Smart Sharpen Filter
- #94. Using High Pass Sharpening
- #95. Sharpening Selectively
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#94 Using High Pass Sharpening
High pass sharpening is an advanced sharpening technique that is easy to learn and apply. I have found this technique to be especially helpful for visual learners who like to see how the sharpening is being applied in a step-by-step fashion.
By way of introduction, this technique uses the High Pass filter, which was originally created for extracting line art and large black-and-white areas from scanned images. However, let’s be creative and use this filter to generate a grayscale image, which retains edge details and removes low-frequency detail. This grayscale image is exactly what you’ll use to sharpen images. You will find this sharpening technique helpful when you have an image with strong edges that need to be sharpened.
To apply high pass sharpening:
- Copy the Background layer by choosing Layer > Duplicate Layer. Name the duplicate layer High Pass (Figure 94a).
- Choose Filter > Other > High Pass.
- In the High Pass dialog box, set the Radius to a low value (Figure 94b). The exact amount will vary based on the image size and resolution. Try a low filter setting of 1.0. The level of grayscale in your image should look something like the one in the preview window of Figure 94b.
- Click OK to apply the filter.
- Change the blending mode of the High Pass layer to Soft Light (or Hard Light for a stronger sharpening effect). Lower the Opacity to fine-tune the amount of sharpening. Typically, the Opacity amount will be below 50% (Figure 94c).
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