Landscape photographers learn early to reach for small apertures. Logic seems to support it: a narrower opening, more depth of field, everything sharp from foreground rock to distant ridge. Set the aperture to f/22, lock focus, press the shutter. The problem is that physics disagrees with this workflow, and the disagreement shows up in your images as a kind of softness that looks almost like camera shake — but isn’t.
What Diffraction Actually Does to a Light Wave
When light passes through an opening, it doesn’t travel in perfectly straight lines. The edges of the aperture blades interrupt the wavefront, causing it to bend inward — a phenomenon called diffraction. This is not a lens defect, not a sensor limitation, and not something firmware can correct. It is a fundamental behavior of waves encountering an obstacle.
The practical consequence: as the aperture opening shrinks, diffraction spreads the light from a single point in the scene across a larger area on the sensor. That spread is described by an Airy disk — the central bright spot surrounded by faint rings that you’d see if you imaged a perfect point source of light. At f/8, the Airy disk on a typical full-frame sensor is small enough that it falls within one or two photosites. At f/22, it has grown enough to cover several photosites simultaneously, and the image loses resolution accordingly. You’re not recording less light per se — you’re recording blurred light.
The threshold where diffraction begins to limit resolution is called the diffraction limit, and it is aperture- and pixel-pitch-dependent. Smaller pixels — which high-megapixel cameras have — hit that limit at larger apertures (numerically lower f-numbers) than sensors with coarser pixels. A 60-megapixel body can start showing diffraction softening at f/11 or even f/8, depending on whose analysis you follow. A 24-megapixel body with larger pixels may tolerate f/16 before the effect becomes clearly visible in a 1:1 comparison.
The Diffraction Limit Is Not the Same on Every Camera
This is where things get camera-specific and worth thinking through before you build a habit.
A useful way to think about it: your pixel pitch is fixed, and diffraction blur grows predictably with f-number. When the diffraction blur circle grows large enough to span more than roughly two pixels, resolution starts declining. The exact crossover depends on the sensor’s pixel pitch, which you can look up in your camera’s specifications — it is typically listed in micrometers (µm). Sensors with a pixel pitch below around 4 µm tend to diffract-limit earlier than those above 5 µm.
What this means practically:
- High-resolution mirrorless bodies (36 MP and above on full-frame, or any recent high-density crop sensor) will often show measurable diffraction softening at f/11–f/13
- Mid-resolution bodies (20–30 MP full-frame) typically begin showing it around f/13–f/16
- Lower-resolution bodies (under 20 MP, or sensors with larger pixels like many medium-format backs) may stay clean to f/16 or a little beyond
- Smartphone sensors, with their extremely small pixel pitch and tiny apertures, are already operating at or near diffraction limits under many lighting conditions — one reason computational sharpening is baked into mobile camera pipelines
None of these are sharp cutoffs. Diffraction softness accumulates gradually. The point is that f/22 sits well past the diffraction limit on essentially every current camera, and f/16 is past it on many high-resolution bodies.
Depth of Field Is a Red Herring at Small Apertures
The reason photographers gravitate to f/22 is usually depth of field. At that aperture, hyperfocal distance shrinks enough that nearly everything from a couple of feet to infinity is technically within the depth-of-field range. This is genuinely useful — or would be, except that diffraction has already cost you more resolution than the extended depth-of-field gains.
Put differently: yes, more of the scene is nominally in focus at f/22. But the absolute sharpness of any given point in that scene is lower than it would be at f/11, because the diffraction blur is now the dominant limit, not focus precision. You’ve traded peak detail for a wider (but softer) sharp zone.
The standard solution is focus stacking — shooting the same composition at a wider aperture (typically f/5.6–f/11, near the lens’s optical sweet spot) across two or more focus distances, then blending those frames in software. Each individual frame is sharper than any single f/22 shot, and the composite achieves depth of field that rivals or exceeds what stopping down alone would give you. Focus stacking is the approach most fine-art landscape photographers use for prints where pixel-level sharpness matters, precisely because f/22 stacks up poorly against a blended set of optically sharp frames.
If you want to understand where sharpness actually goes and why, the aperture-diffraction relationship belongs in the same conversation as our article on what f/8 really costs you on a 400mm wildlife lens — different end of the aperture range, same underlying physics applied to a different tradeoff.
Finding Your Lens’s Actual Sweet Spot
Every lens has a range where it performs best — not wide open (where aberrations and vignetting tend to peak) and not stopped all the way down. For most modern prime lenses and high-quality zooms, that sweet spot sits somewhere between f/5.6 and f/11, though it varies. Finding it requires a controlled comparison: shoot a stationary, high-contrast target from a tripod at each aperture stop and examine the results at 100% in your processing software. Look at the center and corners separately, since some lenses sharpen at the center first and corners later as you stop down.
This kind of test tells you where your specific lens, on your specific sensor, actually resolves best. It is a more reliable guide than any general rule.
A useful mental model: the optimal aperture for sharpness sits where diffraction hasn’t yet softened the image, but optical aberrations from shooting wide open have already diminished. That window is usually wider than photographers expect — often two to three stops — and it almost never extends to f/22.
When Small Apertures Still Make Sense
None of this means f/22 has no role. There are specific situations where it remains the right choice:
- Starburst effects on light sources — aperture blades create pronounced star patterns at small openings, a deliberate aesthetic choice in architectural and night photography
- When diffraction softness is acceptable — if the image will be viewed at modest size or on screen, and depth of field is genuinely critical, the softening may not be visible at your output resolution
- When you have no option — flash sync speeds, neutral density filter limitations, or shooting conditions that force exposure choices can land you at small apertures regardless of sharpness preference
Outside those cases, stopping all the way down tends to cost more in resolution than it recovers in depth of field. The habit of reaching for f/22 as the “safe” choice deserves scrutiny.
The practical next step: check the pixel pitch of your specific camera body — it is in the technical specifications on the manufacturer’s product page — and run a simple aperture series on a textured surface from a tripod. Compare the frames at 100% in your image processing software. The aperture where the center sharpness peaks is your benchmark. From there, you can decide how much depth of field is worth trading for it. For more context on the image-quality tradeoffs that appear across the image-making pipeline, see our Image Quality section.