f/16, the unloved f-stop, is far more useful than we give it credit for.
As photographers, it’s easy to get in our own heads and overthink which aperture to use. On one hand, there’s the classic saying – “f/8 and be there.” On the other, modern lens reviews almost always conclude that the sharpest aperture is around f/4 or f/5.6.
But what aperture does no one seem to like, and certainly not recommend that you use if you can help it? f/16.
Review after review shows pitiful lens performance at f/16, often worse than wide open. The farthest any self-respecting photographer would dare to go is f/11, or so says the popular wisdom.
Adding to this perception is the fact that many lenses max out (min out?) at f/16. When you reach that aperture, you get the sense that Nikon and Canon are park rangers grabbing you by the shoulder and saying, “Whoa, that’s far enough, buddy,” as you approach the edge of a cliff.
If you’re wondering why f/16 gets a bad rap, it’s not hard to explain. Diffraction is high at that aperture – light waves bending and interfering with one another as they pass through your aperture – meaning that photos at f/16 just aren’t as sharp as they can be.
This diagram shows the levels of diffraction you can expect at various apertures, all the way to an unreasonable f/32 (click to see the differences more clearly):
Personally, I love f/16. (Though I’m speaking as a full-frame camera user; divide 16 by your crop factor to get the equivalent for your camera system.)
I’ve written reviews for Photography Life where I talk about a lens’s sharpness getting worse by f/11 and especially f/16. Yet every time I write something like that, I start grinning maniacally and whispering excellent like Mr. Burns.
Why? Because those apertures are where I’m planning to make my last stand – loss of sharpness be damned.
Case in point: My “best-of” collection in Lightroom currently has 84 photos. I took 20 of them at f/16, the most of any aperture. Second most is f/11, where I’ve taken 11 of my favorite photos.
Of course, I’m a landscape photographer, so this skews the numbers quite a bit. If you’re a documentary or portrait photographer, this article probably isn’t for you. Stick with f/2.8 or whatever aperture you prefer. Then pat yourself on the back for avoiding any significant sharpness loss from diffraction.
That said, how much sharpness loss are we really talking about with f/16? To put things into perspective, take a look at the following lens chart. It’s from the Nikon 20mm f/1.8G, a sharp lens that’s popular among landscape photographers:
As you can see, center sharpness on this lens is the worst at f/16. Sharpness in the corner is only a tad better; f/16 beats the numbers at f/1.8 and f/2, but it’s worse than everything from f/2.8 and beyond.
It doesn’t seem like there are many redeeming features to f/16. But that’s missing a couple important points.
For one, don’t just pay attention to maximum sharpness numbers. Pay attention to sharpness consistency across the frame – the difference between center and corner sharpness. By that measure, although f/2.8 is sharper overall than f/16, it’s not a great aperture to use; the disparity between center and corner sharpness is just too large – probably enough to stand out to a discerning viewer.
Instead, the best aperture on the Nikon 20mm f/1.8, taking both consistency and overall sharpness into account, is arguably f/8 – even though center sharpness is higher at three other apertures. You might argue that f/5.6 is a better aperture overall, and that’s true in total numbers, but the extra sharpness in the center of the frame at f/5.6 is not necessarily preferable if it makes the corners visibly worse by comparison.
Admittedly, though – even by a generous definition – f/16 is a step down in image quality from most of the other apertures. But that doesn’t mean you should avoid it. Aside from its excellent consistency from corner to corner, f/16 is worth using because of one important reason: depth of field.
Let’s say you want maximum foreground and background sharpness in a photo you take with the Nikon 20mm f/1.8. You’re focused 6 feet / 2 meters away, and the nearest object in your photo is 3 feet / 1 meter away (because you followed the double the distance method optimally).
I think you’ll agree that this is a pretty reasonable situation – certainly not an “extreme” scene where you’re focused on something that’s almost touching your lens. But in this scenario, which aperture should you use to maximize foreground and background sharpness?
Too wide an aperture loses sharpness because there’s not enough depth of field, while too narrow an aperture cancels out the increased depth of field by adding too much diffraction. Mathematically, though, there is an answer – and in this case, it’s f/13.
That’s a lot smaller than most people would think. A 20mm lens has a lot of depth of field compared to longer lenses, and focusing six feet away isn’t exactly crazytown. Yet, to maximize foreground and background sharpness, f/13 is indeed the way to go.
If your answer in this case is “f/8 and be there,” you’d lose about 17% of the maximum possible sharpness in both the foreground and background. If your answer, instead, is “f/16 and be there,” you’d only lose about 5% (calculated using George Douvos’s charts here).
The calculation shifts even more in favor of f/16 as you use longer and longer lenses. 20mm is pretty clearly a wide angle, which gives it some extra depth of field. But what if you wanted to use a 35mm lens instead – also a popular choice for landscape photography?
With that focal length, f/16 is optimal when you’re focused a very typical 12 feet away (3.7 meters). And it’s not far from optimal even if you’re focused on something that’s a whopping 20 feet away – only a 7% loss of sharpness versus the ideal aperture of f/12.
A lot of photographers will use a 35mm lens for landscape photography and casually pick f/8 or so, thinking they’re getting a lot of sharpness. But unless you’re focused 50 feet away or more (15 meters), f/8 doesn’t get you the sharpest photos. A smaller aperture does instead.
That’s why f/16 is so great.
Often, photographers don’t realize just how little depth of field they can get at f/4, f/5.6, or even f/8. I’ve seen plenty of photographers get blurry corners even at the supposed “sharpest” aperture on their lens. The reason? The lens isn’t blurry at that aperture. Their corners are just out of focus.
I’m not saying that f/16 is a sharp aperture in and of itself. It’s not. But if you’re photographing a three-dimensional scene, and you want good definition from front to back, it’s very often (I’d even say most of the time) a better aperture than f/4 or f/5.6 – even if it doesn’t score as well on a flat test chart.
A photo taken with good technique at f/16 still has pretty wicked sharpness. Sure, there’s diffraction, but it’s not bad enough to ruin a photo. (If your photo is too blurry to print large at f/16, it’s not diffraction that caused the problem.) Focusing errors and motion blur are, by far, the more likely culprits when your photo isn’t sharp.
Indeed, if focusing errors are what plague you, f/16 can actually help your sharpness. All that extra depth of field smooths out focusing errors (and some lens issues like field curvature) to make for better results than you’d otherwise get. In a way, it minimizes the chances that something can go wrong in your landscape photo.
That said, I definitely don’t recommend using f/16 as your default. I don’t recommend using any aperture as your default, because the best aperture changes wildly from scene to scene (and if maximum sharpness is your main priority, you’ll usually be focus stacking anyway). If I did have to pick just a single “best” aperture for daytime landscape work, I’d probably lean f/11 rather than f/16 anyway.
But the horrors of f/16 are way overblown. If your foreground is close to your lens, or you’re shooting landscapes with a telephoto, small apertures will improve your image quality far more than they harm it.
So, the next time that you see warning signs about the impending sharpness abyss, tell your lens company that you know better and walk right up to the edge. The photos you capture will be worth it.