Digital Photography Tips and Techniques

High pass sharpening is one of the popular sharpening techniques along with unsharp mask (USM) and lab color sharpening used by Adobe Photoshop users.

Capture NX is Nikon’s NEF raw workflow software and it has many innovative processing technologies. The best thing about it is that it offers most of what raw shooting photographers need without breaking the bank. Here is a tutorial on how to do the high pass sharpening using Nikon Capture NX.

1. Get the photo ready for sharpening

Go through your normal workflow in Capture NX including resize/crop to the point it is ready for sharpening. It is recommended to apply sharpening as the last editing step. The following photo is used for illustration purpose. To start, set the view to 100% (Ctrl-Alt-0) so you will be see the sharpening details.

2. Apply the high pass function

From the menu bar, go to “Adjust->Focus->High Pass …” as shown in the following screen capture.

Once you select the high pass function from the menu, the photo will be turned into a gray scale image similar to the following .

You will also be presented with a simple high pass setting dialog box with radius as the only option. The default for radius is 1. Going to value smaller than one does not seem to do anything visible, while you can see the details in the image changes as you drag the radius slider to the right (larger radius).

The high pass filter function attempts to block all image details, except from those details with very strong edge definitions. This results in a neutral gray image with only the edges of the original image appearing in the default normal blending mode. For sharpening purposes, the radius should remain small (1 to a few pixel depending on the final image size and details) so the sharpen happens at the very fine edges. Larger radius from tens to 100 px can be used for contrast enhancement purposes (will be discussed in a separate article).

For now, you can only drag the radius slide around and while you can see something change in the photo but it is most likely not what you are expecting. This is because the default blending mode (normal) is used. Since you really cannot change the blending mode here you can simply click OK to continue.

3. Fine tune the high pass sharpening

If you have not already done so, go to “Windows->Edit list” to open the edit list. Mine looks something like the below.

Expand the high pass item (item #4 in this tutorial) in the edit list by clicking on the small triangle on the left. You will see something like the following. Now you have two options under high pass: (1) the Opacity option, and (2) high pass option.

First, open the opacity option by clicking on the small triangle. Once opened, the triangle will point to the left and you will see the opacity option dialog box. Change the options so yours will look like the following. For sharpening purpose, we will only operate on luminance channel (chrominance channel slider is set to 0). The blending mode should be overlay. Click OK to continue.

Now you can open the high pass option (radius) setting dialog box again to experiment with the radius setting until you are satisfied with the result. In addition, you may also go back to the opacity option and play with the luminance channel opacity slider.

4. The result

Below is the final result from this tutorial. It may seem to be very subtle because I intentionally used a small radius of ~2px. Like all photo enhancements, it is easy to overdo the effect and make things unnatural.

5. Final words

I hope you enjoy reading this tutorial on high pass sharpening using Nikon Capture NX. If you have any comments or suggestions, please feel free to use the comment box below.