High Pass Sharpening
A Photoshop Tutorial
Every photographer as well as artisans of all sorts know how important it is to have an extra specialty tool available for when things don't quite work out the way you expect them to. Photoshop's High Pass Filter is one of those tools. Let's see how to use it.
Unsharp Masking is the way that everyone who works with digital image processing knows to sharpen their files. Of course the use of this ill-named tool has nothing to do either with masking, or unsharpness. It's just a carryover from the days when an unsharp negative was sandwiched with a sharp one to enhance edge contrast. And that is in fact what the Unsharp Mask tool in Photoshop does, it increases edge contrast. (For a look at the best methods for doing Unsharp Masking have a look at my tutorial Instant Photoshop.)
But, as useful as it is, the USM tool has problems, and one of these is that it also increases any noise present in the file. Particularly noisy photographs therefore can suffer when USM is applied.
Take a (High) Pass
On the Layer palette select your Background Layer and right click. Select Duplicate Layer.
- With this new layer highlighted select Filter / Other / High Pass. Set the Radius to 10 and click OK.
- Zoom into your image to Actual Pixels level so you can better see what you're going to do next.
- Go back to the Layer Palette and select Hard Light from the left drop down.
- Now go to the Opacity Slider and select a level of sharpening that seems best to you. Usually something between 20% and 70% will be best.
That's all there is to it.
What I particularly like about this method of sharpening is that it can be undone even after the file has been saved. This is because the sharpening is done on a separate layer not on the original background layer. You can also click the eye beside this layer on and off to see the effect at any time.
Thanks to the Australian magazine Design Graphics for drawing this technique to my attention.