Advanced High pass sharpening

Today I'm going to write something about Photoshop technique known as High Pass sharpening. It's very useful and effective way to sharpen your photos. I have to say it's not the only way, of course. You can sharpen your images more quickly with Unsharp Mask or Smart Sharpen filter, or more sophistically with custom masks, channels etc. There are many ways to sharpen an image and I think none of these can be used at any time. Some photos needs different way to sharpen. It's also dependent on usage of this sharpened photo -- you should use different way for sharpening an image to be viewed on screen and different for printing.

Traditional High Pass sharpening is done very easily. You create High Pass layer and set it to Overlay blend mode. But this can sometimes lead to increased leved of saturation. If you want to avoid it, you should use this advanced version of High Pass sharpening, which uses traditional High Pass layer as mask to new layer, which is set to Luminosity blend mode.

High Pass sharpening is based on High Pass filter. I have prepared these 15 steps to get you easily through this process:

1) load the file you want to sharpen. I will be using image above.

2) make new layer from background layer via copy (ctrl+j)


3) select from menu Filter->Other->High Pass...


4) set about 3 pixels and click ok


5) select from menu Image->Adjustments->Threshold...


6) set Threshold Level to about 125 (black color means "this is going to be sharpened" and white color means "this is not going to be sharpened" -- you can use brush tool to manually fine tune this)


7) click on channels tab and load RGB channel as selection (ctrl+click RGB channel or press little button on the bottom of the channels palette)


8) duplicate background layer (you can drag and drop this layer on little New layer button in bottom of the palette or click with right button of your mouse)


9) move your new copy of background layer to the top of the layers list


10) disable visibility of Layer 1. You have loaded selection in step 7, remember? Now we are going to use it. Make mask to your new copy of background layer. Click little button on the bottom of the layers palette.


11) make sure, you have selected this newly created mask


12) blur that mask with Filter->Blur->Gaussian blur, set it to 1.5px


13) select layer content (not its mask) and make Filter->Sharpen->Unsharp Mask (or Smart Sharpen if you prefer). Set it to about 80%-120%, radius 1.5px, threshold 1.


14) change blend mode of this new layer to Luminosity


15) clean up mess and delete layer 1, you are done


You can view before/after just by hiding new layer. You can easily create action of this procedure. In comparison to Unsharp Mask this one is better with noisy images, because it doesn't sharpen pixels, but edges (these edges are made by High Pass filter). More information about this technique can be found at Adobe web page.

Here you can see comparison (zoomed to 100%) of this technique to original and to Unsharp Mask:

1) original:


2) advanced High Pass sharpening:


3) Unsharp Mask:


I think Unsharp Mask is loosing some color gradients here and makes photo a little oversharpened (it's been set to 110%, 1.5px, 1 -- same values as in High Pass sharpening). You can also add more sharpening to High Pass procedure, just with different selection of Threshold or with different High Pass filter values, etc. It depends if you want to sharpen that picture for printing or not. Good luck.