With Adobe Photoshop, there’s numerous ways to do any one thing. And so it is with sharpening.
High Pass filter
When I’m sharpening, I often use the High Pass filter in Photoshop. This is not found with the other sharpening tools, but instead is found under the Filter menu.
High Pass filters are designed to detect edges and highlight them, ignoring areas that are not edges. Perfect. We don’t want to sharpen someone’s skin, the night sky that has no stars, or smooth surfaces, after all! I’ll discuss using a High Pass filter two different ways, the second way with luminosity masks.
Above: zooming in to 200% in Photoshop to see the effect of sharpening using a High Pass Filter.
Five easy steps using High Pass filter to sharpen your image
1. Create a new layer
This will be your High Pass sharpening layer. Try to apply sharpening as the very last step before finishing your photo.
2. Apply the High Pass filter
Go to Filter > Other > High Pass. Your image will turn gray.
3. Adjust the High Pass filter radius
The dialog box is simple to use. Simply adjust the radius. As you might guess, this simply affects the width of the edge. How far out do you want the sharpening effect to extend? Adjust this until it looks good.
You mostly want to see the edges that you want to sharpen. I find that a relatively small radius value, perhaps between 1.8 to 3.0, often looks the most pleasing. Press OK.
4. Change the filter’s blend mode
It’s still gray! Not to worry. In the Layers tab at the bottom right of Photoshop, change the blend mode from Normal to Overlay.
You should immediately see the original photo, albeit a sharpened one. You may also may try other blend modes, such as Soft Light, Hard Light, Vivid Light or Linear Light. I usually go with Overlay or Soft Light, but I’ve used all of these blend modes at some point.
5. Modify what gets sharpened further using a Layer Mask
Are there any parts of the image in which you want to have less sharpening? If so, you can address this non-destructively using Layer Masks.
To get started, go to Layer > Layer Mask > Reveal All. This will produce a white Layer Mask. Highlight the white Layer Mask by clicking on it, and then begin using your Brush tool with a black color and “paint” the areas that you don’t want to have sharpened. Remember, for Layer Masks, white reveals, black conceals.
Bonus tip: Sharpening using luminosity masks
Now that we’ve touched upon Layer Masks, let’s go one step further.
You can sharpen while using luminosity masks, which targets edges even more specifically. For instance, I like to try to target the edges around the foreground object. I can do this by selecting areas based on brightness or darkness, then create a High Pass filter from that.
I use Lumenzia for luminosity masks because it’s easy to use and effective.
Here, I’ve selected a zone that best accentuates the building. I then select Sharpen. One of the choices is to create a High Pass filter based on the brightness/darkness zone, so that’s what we’ll do.
This also creates a Layer Mask automatically. Notice that this one is different from the purely white Layer Mask. It’s also masking the light and dark areas that you specified.
From here, if I want to “paint” out areas that I still don’t want sharpened, I can do so, just as I did above.
You don’t need to use Layer Masks. As I mentioned, there’s always several ways to do things. And there’s even several ways we could target what we want with Lumenzia or other luminosity masks. I think part of it is that I find “painting” on the Layer Mask to be quick, intuitive and somehow oddly pleasing. It makes me feel more connected to the image that I am creating.