Edge Sharpening Thoughts

Fresno Bonsai Exhibition, Nikon D810 with Sigma 35mm f/1.4 Art Lens at f/4.8 1/180 sec ISO 64 handheld

by Rich Seiling

Edge sharpening has become a popular technique, but I think it’s better for film scans than for digital camera images. Let me tell you why, and how it can be adapted for digital camera files. 

Edge sharpening goes way back. I first learned to do it around 1999 from Bill Atkinson, one of the first Apple employees and the reason windows in the mac interface work the way the way they do , and the mouse, and a whole host of other patents. 

Atkinson created an edge sharpening action script for Photoshop because of the grain in film scans. When you sharpen a film scan, you also sharpen the grain. Edges are more tolerant of heavy sharpening than flat even toned areas like sky. So Atkinson introduced people like Galen Rowell and a host of other well known landscape photographer to this technique, and it made it’s way into our toolbox. Atkinson’s tool has been an incredibly important contribution to the art of printmaking.

But fast forward to today. Is sharpen edges still the right technique? Low ISO digital images do not suffer from the grain problem of film. And edges are already sharp because of the nature of digital capture.

I still use a variation of Atkinson’s script today, but I use it inside out. I find that sharp edges in a good digital capture need little, if any, additional sharpening. It’s easy to make them halo and crunchy, and I don’t like that look. But smooth tonal areas often suffer from a lack of apparent sharpness. Part of this is because of the Bayer filter in our digital cameras. The pixels in our photos are only seen through one color filter, and the actual color is reconstructed by interpolating neighboring pixels viewed through different color filters. This does some stuff to non edge/smoother tone areas that degrades the apparent sharpness.  

Here’s an edge mask I created from the red channel of the bonsai photo.

Edge Mask

My approach with digital camera images is to use the sharpen only edges scrip to select the edges, and then I invert that selection so that I can sharpen only non-edge areas, which I find can take much more sharpening than the edges. 

These gifs show a 100% actual pixels section of these images with no sharpening, edge sharpening, and non-edge sharpening using the settings below:

In the top photo, look at how the edges of the leaves and the texture of the tapestry on the right respond to different sharpening approaches. And in the bottom photo, again look at the leaves, as well as the woven grass mat and the edges and detail in the wood stand.

Sharpening settings used for edges and non-edges.

As you can see, the non-edge areas handle this amount of sharpening better than the edges. In fact, with edge sharpening, I find the edges of the leaves over-sharpened at this setting, and part of the wood stand is over-sharpened as well.

Do I sharpen every image this way? No. But I do use this technique a lot, and the understanding of how and why is what guides my choice of tools. How, and how much to sharpen is very much a preference. Everyone has a different flavor. Lately I find myself applying less sharpening than in the past, and trying to closely replicate the kind of image quality and appearance you see in large format prints by photographers like Ansel Adams. How you use the tool is up to you!

Why You Should Make Prints

Are you making prints on a regular basis? Why? Or why not? 

I think printing should be a regular part of your photography. Nothing will test your photographs more, stretch your abilities, and force you to learn new photography skills, than the process of making prints. 

I’ll go so far to say that, if you can consistently produce fine quality prints from your photographs, you will have successfully mastered key components of the craft of photography, and you will be equipped to explore even greater depths of the art. 

First, you have to understand that prints are the ultimate expression of a photograph. 

Stop thinking that what your monitor or device shows you is what your photo really looks like. The screen is not even close to the accuracy of a print.

Professional printing devices are capable of producing a much wider range of colors (color gamut) than a screen can. They are capable of higher resolution, greater detail, more delicate highlights, and delicate shades of gray in black & white. It’s the difference between a flawless live performance of your favorite music, versus a YouTube video of it from a crummy phone. 

Because of this, the print is unforgiving. It will show every flaw and every error in judgement, exposure, focusing, color balance and processing. It’s not a 1500 pixel square on your phone; it’s the real thing, raw, fully laid bare for all to see. And that’s why it’s so powerful. It will test you, measure you, raise your expectations, challenge you, sharpen you, and make you a better photographer. 

Don’t do it alone. You need someone who has already mastered the skill to guide and critique your progress; to tell you it’s too contrasty, your highlights are blown out, or you didn’t focus properly. This is an integral part of formal photography training that is lost if YouTube is your only teacher. 

Take a class at a local college, go on workshops, and share your work at local photo clubs. Seek out people who make prints you admire, and beg, borrow, or buy time with them to be mentored. Some of the best photographers in the world are easily accessible through workshops. Take advantage of that. 

Then find museums and galleries close to you, get on their mailing lists, and go look at prints regularly. Seek it out when you travel. Develop a mental impression of what you think a great print should be. See how artists handle shadows and highlights, color, focus, and paper choice to make their expression. 

Lastly, make prints regularly. You’re going to learn more working on a fifty prints in a year than you will just ten. Don’t get caught up in what’s “print worthy” or not. If you think there is something there, print it and start working the process. Hang them on the wall, live with them, and see if they stand the test of time or need to be reworked, or abandoned. Start with 8×10 prints then work your favorites up to larger sizes. Fill your walls, and your friends! Give them as gifts, and let others enjoy them.

Making prints is the fast-track to improving your photography and refining your craft, making you into an even better photographer than you already are.