I sometimes post my camera settings here on the blog, and I’ve had many people ask me why I often use f/16. Is that the sharpest aperture on my lens? (No.) Don’t you get diffraction at f/16? (A little bit.) Is it for depth of field? (Bingo!)
As many of you know, most lenses are sharpest at middle apertures – generally around f/5.6 to f/11, depending on the lens.
Better lenses will perform decently at wide apertures like f/2.8 or f/4, but usually the corners are softer compared to the middle apertures. On the other end of the spectrum, at smaller apertures diffraction causes all lenses to get softer over the entire image (not just the corners).
But you get more depth of field at smaller apertures. That is, more of the scene will be in focus from front to back. And that’s a very important consideration with landscape photographs, where you usually want the entire image in focus – near, far, and everything in between.
When I don’t need much depth of field I pick the sharpest aperture for the lens I’m using. On some of my lenses that’s f/8, on others it’s f/11.
But when f/8 or f/11 isn’t enough to get everything in focus, I use f/16. Yes, I get some diffraction at f/16, but that’s preferable to having the foreground or background – or both – out of focus. And with my lenses the diffraction is minimal at f/16. I’ve made very sharp 30-by-40-inch prints from images captured at f/16 on my 36- and 42-megapixel Sony cameras. At f/22, however, the diffraction gets noticeably worse. So I avoid f/22 unless that’s the only way to get everything in focus. I’d rather use a wider aperture and focus-stacking to get everything in focus, but sometimes wind makes focus-stacking impossible.
So that, in a nutshell, is why I often use f/16: it’s a small enough aperture to get lots of depth of field, but not so small that diffraction seriously degrades the image. If you want to delve into the details a bit more, read on.
The Fine Details
Technically, diffraction can be detected at f/11 – maybe even f/8 on some very-sharp lenses (coupled with high-resolution cameras). But at f/11 the diffraction is usually barely noticeable. It becomes more noticeable as you stop down to f/16 and f/22.
So when does diffraction become so bad that it seriously degrades the image? That’s a bit subjective, of course, but for me, with my lenses, I’ve found that f/16 is reasonably sharp, while f/22 is distinctly softer. So that’s my cutoff point. Of course I have some very good lenses, and not every lens will perform well at f/16. But that’s one of the main reasons I use those lenses: because they’re good at f/16. If a lens isn’t sharp at f/16 it’s pretty useless to me. Unfortunately, many of the websites that perform lens tests don’t post results for f/16; they skip from f/11 to f/22. What’s with that? But if a lens performs well at f/11 it will probably also perform well at f/16. And I never rely on those websites anyway. Yes, they can help me decide whether a lens might fit my needs, but I rely on my own tests and my own eyes.
One aspect of this discussion that often gets overlooked is image sharpening. The slight softening created by diffraction at f/11 or f/16 can be largely mitigated by using the appropriate “capture” sharpening settings in raw-image processing software. In Lightroom and Adobe Camera Raw, the default sharpening settings are geared to general photography, not landscapes. Here’s what those default settings look like:
However, the leaves, twigs, grasses, and other fine details in landscape photographs look sharper with a lower Radius, higher Amount, and higher Detail. I start with the Amount at 40, Radius at 0.5 (as low as possible), and Detail at 50, like this:
But that’s just a starting point. Before printing an image, or before exporting it out of Lightroom into Photoshop or another program, I’ll fine-tune those settings and optimize them for the particular image. With low-ISO images that usually means increasing the Amount and Radius.
Here’s an example, a photograph from Colorado made with my old Nikon 50mm lens at f/16:
The 100% (1:1) screen shot below shows Adobe’s default settings on the left. The right-hand screen shot shows the trees after I’ve optimized the sharpening settings – in this case pushing the Amount to 60 and Radius to 0.7, while keeping Detail at 50 and Masking at 0 (click on the image to actually view at 100%):
With Adobe’s default settings the trees look a little soft. But increasing the Amount, lowering the Radius, and increasing the Detail made the trees look much sharper (again, click on the image to view at 100%). Keep in mind that this 100% screen shot shows a tiny part of a 42-megapixel file. With those optimized settings this would make a very sharp 30-by-40-inch print.
So am I concerned about diffraction? Yes, of course. But I don’t hesitate to use f/16 when I need more depth of field, because I know I can make large, sharp prints from those images.
— Michael Frye
Michael Frye is a professional photographer specializing in landscapes and nature. He is the author or principal photographer of The Photographer’s Guide to Yosemite, Yosemite Meditations, Yosemite Meditations for Women, Yosemite Meditations for Adventurers, and Digital Landscape Photography: In the Footsteps of Ansel Adams and the Great Masters. He has also written three eBooks: Light & Land: Landscapes in the Digital Darkroom, Exposure for Outdoor Photography, and Landscapes in Lightroom: The Essential Step-by-Step Guide. Michael has written numerous magazine articles on the art and technique of photography, and his images have been published in over thirty countries around the world. Michael has lived either in or near Yosemite National Park since 1983, currently residing just outside the park in Mariposa, California.