Sharpen makes photo sharp, but how?
Almost all post-processing programs offer ‘Sharpen’ to make photo crisp and sharp. Sometimes different naming used, for example, ‘Unsharp mask’ in Photoshop which is actually a sharpen. No matter what name, Sharpen works basically in 2 steps;
- Extract the ‘outline’ of image
- Increase the contrast of the outline to make image crisp to viewers.
How to extract the boundary line and how to apply contrast is the difference of various sharpen method.
High Pass filter
The high pass filter is a part of sharpen process, ‘extracting the outline of an image’, and available as a filter.
That is, if photographer get the image outline, he/she can arbitrarily make the line stronger & darker, or weaker & smoother, or erase a certain part of outline altogether. Therefore using Sharpen in the program is using pre-defined algorithm by company, while using High Pass filter is controling the degree & area of sharpening for photographer themselves.
- Before and after High Pass filter
Part of a 100% enlarged image. I applied strong effect to show difference of High Pass filter clearly in here. Personally I prefer weaker than this…
How to do High Pass filter
1. Copy background layer : CTRL + J
2. Select Filter > Others > High Pass filter in the Photoshop menu.
A pop-up window appears as below and you can enter a number in Radius. In this example, I entered 12.5 Pixels …
3. In this phase, the screen still shows gray image seen in the High Pass filter. (Please note current layer is set to ‘Normal’ and the opacity is ‘100%’ as a figure below). Change Normal to Overlay.
4. The screen shows photo image normally when the setting change to Overlay.
From here, you can adjust ‘Opacity’ to adjust the degree of the High Pass filter effect. In the example below, the opacity is set to 70%.
End of work.
Easy Photoshop… :- )