This is the first part of a three-part series that describes and demonstrates the three creative applications of the high pass filter inside of Adobe Photoshop Mac. If you haven’t already read the introduction then I recommend checking it out here: introduction to high pass.
Why you should sharpen your images
Sharpening your images has become a necessary evil in the digital age. Because of the nature of the digital image capturing process, our photos come out flatter and blurrier than if we had taken them using film. The image above demonstrates the difference that sharpening can have on an image. I haven’t gone mad and started randomly taking photos of brick walls, I have chosen the wall as a subject because:
the 2-dimensional surface makes for better comparison as it eliminates any difference in depth of field.
- b) the texture of the bricks benefits from the sharpening process and highlights the difference it can make.
Sharpening an image doesn’t have to be as boring as a brick wall, rather it can be creative and intuitive. One of the best ways to sharpen your images in a creative way is to use the high pass filter and here are four reasons why:
Four reasons you should use the high pass filter to sharpen your images
It is easier to use than the unsharp mask and smart sharpen filters. It self-thresholds. (Any areas on the image without edge detail is left untouched. This makes high pass more useful for sharpening portraits or files that contain a lot of noise) Works with blending and opacity modes. (Through these methods the user has control over the intensity and attenuation of the filter) It doesn’t clip. (The unsharp mask and smart sharpen filters use contrast to sharpen, sometimes this results in clipping shadow and highlight detail, the high pass filter doesn’t suffer the same problem)
My personal favorite of these is the first. The filter itself is simple and the user can use blending modes and opacity settings to adjust the effect. This makes the high pass filter more intuitive control. And since Photographers are very attuned to the visual and aesthetic of imagery this filter suites their style of control. In other words, the high pass allows you to make adjustments based on aesthetic not ‘by the numbers.’
In practical terms, however, the high pass filter is more valuable since it works best on images with low frequency. The filter self-thresholds, or in other words, it targets the areas in an image that has high detail and turns the areas of low detail to grey. When combined with a blending mode you can hide the grey areas and only show the darker and lighter regions of the high pass layer. Essentially this makes high pass a valuable tool for sharpening portraits and also for sharpening images that suffer from noise.
Photoshop video tuts
This video quickly demonstrates how to use a high pass filter to sharpen images. It is intended to accompany the ‘how-to’ steps below.
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How to sharpen using the high pass filter in Photoshop
Step 1) Duplicate the layer you are working on (Ctrl + J).
Step 2) Go to Filter>other>high pass.
Step 3) Choose a radius setting of between 2 and 5 (don’t be afraid to use a higher number since you can always control this in later steps).
Step 4) Desaturate the layer (ctrl + shift + u).
Step 5) Change the blending mode to either: Overlay, Hard Light, or Linear. These three blending modes progressively make the attenuation of the filter more aggressive.
Step 6) Change the opacity of the layer to control the intensity of the filter.
That’s it! This is actually quite an easy and non-technical tool even though the process that happens behind the scenes is. Using this method you can easily control sharpening through a more or less visual style and that is why I find Photographers are more comfortable with it.
Notes on Zoom settings
I recommend making these adjustments at the pixel level so that you can better see the changes as they occur. To do this zoom in to 100% or press (ctrl + 1). Always check to sharpen at 100%, 50%, or 25% magnification. This is because every other zoom setting is not an accurate display of sharpness it is a representation that Photoshop renders and while it may be fine for checking color etc it is not adequate for checking sharpening settings.
Download free photoshop actions
I have created a series of three high pass actions that perform exactly what has been described in the above tutorial. They are a useful way to get started with this technique.
This completes the tutorial on how to sharpen images using the high pass technique. In part two of this series, I’ll demonstrate how to use the high pass filter to soften skin tones in portrait images.