Written on Oct 25th, 2008 by Dave Adams

Posted In: Post Processing

Sharpening Photos With The High Pass Filter

High Pass Filter, Photoshop, Sharpening, Vivid Light

There are times when no matter how good your photography skills are, and how good the equipment your are using is, a photo just doesn’t turn out as sharp as you’d hoped it would. Never fear, all is not lost. With a little post-processing, a photograph can be easily sharpened up to give that perfect final touch you want.

Using Photoshop, there are two options to sharpening a photograph. The first is to use the standard sharpening tool that can be found under Filter > Sharpen > Smart Sharpen. While this filter can result in an acceptable final result, and there is scope for changing the filter parameters, I prefer to use a two step approach using the high pass filter and vivid light.

The example below shows one of my photographs taken at Silverstone race circuit prior to any post-processing. While the photograph is reasonably in focus, its lacking that final sharpness that I wanted.

The unfiltered (unsharpened) photograph

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To correct the photo, I first duplicated the background (original) layer. This allows me to make changes while preserving the original layer, and by using the small eye icon on the layers tab, I can quickly turn layers on and off to see what effect the changes have made.

I have then applied the high pass filter Filter > Other > High Pass with a radius setting of 2 pixels to the duplicate layer. This turns the duplicate layer to gray, with a faint outline of the photo structure visible. Adjusting the pixel radius alters the amount of the photograph tht is visible. The second stage is to convert the layer to vivid light Layers (F7) > Vivid Light. This converts the layer and sharpens the outline of the photograph elements. The result of this can be seen below.

The filtered (sharpened) photograph

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The amount of sharpening that is applied can be controlled by using the opacity slider in the layers tab. As you slide the percentage down, you will see the amount of sharpening reduced. Clicking on the small eye icon on the layer will hide the layer completely, revealing the original layer. Flicking between the two will clearly demonstrate the effect of the high pass filter and vivid light conversion.

It is worth noting at this stage that any sharpening that is applied to a photograph will result in extra noise being introduced to the image. Noise is those ugly pixelated blocks where solid colours break up. In my next post I will discuss methods of reducing the effects of noise in a photograph.

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