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Using the High Pass Filter for Image Sharpening in Adobe Photoshop

There are a lot of different ways to sharpen images in Adobe Photoshop. In this article I’m going to share one of my favorite methods which uses the High Pass filter. Photoshop offers a number of filters and tools dedicated directly to sharpening images, so it might seem strange to use the High Pass filter, but this method has definite advantages for some images.

High Pass sharpening does an excellent job of bringing out detail and it’s my favorite tool for architectural shots. High pass sharpening also allows you a lot of visual control of your sharpening. How the sharpening is applied and even where its applied can all be controlled and adjusted non-destructively after the fact, with real time visual feedback. High Pass sharpening can be very strong and very powerful. This is important to keep in mind because it is very easy to over sharpen your image, especially in areas with very fine details or textures.

Step 1: Duplicate your Image Layer

To get started with high pass filter you need to open your image in Adobe Photoshop. If your image contains multiple layers you will need to flatten the image. Next duplicate your image layer.

Step1DuplicateLayer
Step 1: Duplicate the image layer and make sure that the top layer is highlighted.

Step 2: Select the High Pass Filter

The High Pass filter is an obscure filter buried under the “Other” sub-menu of the Filter menu. It’s generally overlooked and if you’ve ever experimented with it you may have ended up with some strange results. But now we are going to put it to good use in this sharpening process. Make sure the top layer is highlighted and select the High Pass Filter.

Step2FilterMenu
Step 2: Select High Pass from the filter menu.

Step 3: Select the Radius Value

The next step is to select the radius value for the High Pass filter. The radius value is  somewhat subjective but something you will get a feel for with practice. The correct radius value will allow you to see the detail and edges of the subjects in your image. But the line will appear thin and embossed rather than thicker like an actual outline.

Step3HighPass
Step 3: Select the radius value for the Hight Pass Filter.
Step4aSelectRadius
Radius Value of 2.0. This value is too low. The edges of the objects are difficult to see and not all of the detailed areas are visible.

A radius of 4 is a good general starting point. You will find images with very fine textures and large flat areas, or images of people may need a smaller radius. Images with larger textures and architectural images may be able to stand a slightly higher radius.

Step4bSelectRadius
Radius value of 6.4 This radius value is too large. The edges appear thick, like someone traced the outline, rather than embossed, and areas with smaller details start to become muddled.

There is a range of acceptable radius values. Sharpening itself is somewhat subjective and you will still have some additional control over the sharpening after the filter is applied. If in doubt, choose a smaller radius over a larger. As we proceed through the steps if you find that your image contains white fringes or “halos” then it is a sure sign your radius is too large.

Step4SelectRadius
A radius value of 5.2 is selected. This allows all of the detail to appear, but the edges are still thin and embossed in appearance.

Once you have the radius selected click “Ok” to apply the filter.

Step 4: Change the Layer Blending Mode to “Overlay”

Make sure the top layer (the one with the High Pass Filter applied) is highlighted, then change the blending mode to “Overlay”.

If you are happy with the result then you can stop here and enjoy your sharpened image. You can toggle the layer on and off (using the eye to the left of the layers thumbnail image) to better see and evaluate the effect of the sharpening. Look for too much contrast or for white fringing that signal an over-sharpened image.

Step5Overlay
Step 4: Change the blending mode of the High Pass layer to “Overlay.”
Step6OverlayFinal
The final, sharpened image. X100S @ 23mm, ISO 800, 1/1250, f/2.8
BeforeAfter
Final image before and after. The sharpening effect is especially visible in the buildings and the bridges.

Step 6: Adjusting the Sharpening

As I mentioned in the beginning of this article, one of the things I love about the High Pass sharpening method is how adjustable and flexible it is. Here are some ways you can try to adjust and control your image sharpening:

  • If your image appears over-sharpened and you want to reduce the sharpening effect you can simply reduce the opacity of the High Pass layer. This will work unless the problem is that white fringing as discussed earlier. That is caused by using a radius that is too large, and the only way to fix this is to go back and start again with the High Pass Filter set to a lower radius value.
  • If you are having trouble selecting a radius value, you can reverse steps 2 and 4. Changing the blending mode to “Overlay” before applying the High Pass filter will allow you to preview the sharpening effect while you adjust the slider to select your radius value.
  • You can try setting your blending mode to Soft Light instead of Overlay. Soft Light creates a more subtle and lower contrast sharpening.
  • You can add a layer mask to eliminate or reduce the sharpening in certain areas of your image.
oversharpened
This image is noticeably over-sharpened. The radius value of 4.6 I selected is too much for the fine details in the image. There is noticeable white fringing along the wall in the background and the bricks in the foreground have too much contrast. X100F @ 23mm, ISO 320, 1/180, f/8.0
oversharpenedFixed
Here I lowered the radius value to 2.3 and changed the layer blending mode from “Overlay” to “Soft Light” for a more subtle sharpening effect.

Before and After Sample Images

beforeAfter1
High Pass Sharpening Before and After  X-Pro2 + XF55-200mmF3.5-4.8 R LM OIS @ 70.5mm, ISO 1600, 1/2, f/10.0
BeforeAfter2a
Before and Aater High Pass Sharpening. The effect is especially visible in the Capitol dome. X-Pro2 + XF16-55mmF2.8 R LM WR @ 30.2mm, ISO 200, 18/10, f/22.0

High Pass sharpening is a fairly simple process once you are familiar with the steps. It works especially well on architectural images and cityscapes, although I have used the process successfully on many different types of images. If you have tried this method of sharpening I would love to hear your thoughts!

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