A quick post on sharpening drawn from advice I gave a print client today. Sharpening is one of the the places I see photographers have the least confidence in.
The challenge is every image is different and requires different settings. Getting the “correct” settings requires developing an understanding of what you see on screen and what that produces on print. It’s possible to make something that looks too sharp on screen, but looks perfect on the print because a typical screen displays the image at about 93 pixels per inch, but the print can be of much higher resolution, so what you see on screen is in essence “magnified”.
A couple quick tips:
Always view the image at 100% magnification, or actual pixels. This will make sure that one pixel in your image equals one pixel in your screen. When you view your file at some other magnification, what you see on screen is some average of the pixels and can disguise the effects.
2. Don’t use a 4x or 5k monitor like those found on newer iMacs. You need a monitor with a pixel resolution of ~72-110 pixels per inch, or a pixel pitch of around .23-.27mm. In contrast a 4K 24” display has a pixel pitch of ~0.13725mm and resolution of ~180 pixels per inch, which makes the pixels too small to evaluate sharpening easily.
3. Smart Sharpen is not a magic fix. There are many flavors of sharpening. Sharpening is an ingredient, and how, and where you apply it is all preference.
Looking forward to turing this into a expanded tutorial at some point. Until then, experiment!
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.
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.
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!