High Pass Sharpening


Today’s Question: What are the situations when “High Pass Sharpening” [in Photoshop] might be a good choice over “Smart Sharpen” or other methods?

Tim’s Quick Answer: The technique known as “High Pass sharpening” is a technique I consider to be more about emphasizing texture and detail in a photo, rather than sharpening to compensate for softness in a photo. Thus, I would recommend the High Pass technique when you are focused on enhancing detail and contrast in a photo. Note that the technique produces an effect that is very similar to that provided by the Clarity slider in Adobe Camera Raw and Lightroom, among other software.

More Detail: The High Pass sharpening technique gets its name from the High Pass filter in Photoshop. Using the High Pass technique enhances midtone contrast in an image, helping to emphasize detail. If you’re familiar with the basic concepts behind sharpening in most imaging software, you can think of the High Pass technique as being similar to sharpening, but with a higher effective Radius setting.

In other words, like sharpening, the High Pass technique enhances contrast along existing contrast edges in a photo, but it does so across a larger area. In other words, the contrast being enhanced along edges in a photo spreads out from those edges more than would otherwise be the case with typical sharpening.

In fact, with the Unsharp Mask filter in Photoshop you can achieve a result very similar to High Pass sharpening. Simply set a high value for the Radius setting (around 20 pixels or so) and a relatively low value for Amount (around 20% to 50%). And, as noted above, similar results can be achieved with the Clarity slider in Lightroom and Adobe Camera Raw, as well as the newer Dehaze slider in these two software applications.

For those unfamiliar, the High Pass technique is relatively easy to accomplish in Photoshop. Start by creating a copy of the Background image layer, which can be done by dragging the thumbnail for the Background layer to the “Create a New Layer” button (the blank sheet of paper icon) at the bottom of the Layers panel. Then set the Opacity to 50% for this layer, using the control at the top of the Layers panel. Change the blend mode from the default of “Normal” to “Overlay” using the popup at the top-left of the Layers panel. Then choose Filter > Other > High Pass from the menu, and set the Radius value to around 10 pixels, adjusting to taste. Click OK to apply the filter, and then fine-tune the Opacity setting for the Background Copy layer.