Detail:

f/9.0 — Sharpf/8.0 — Sharp

What is this?

Every lens has a "sweet spot" aperture where images are sharpest. If you close the aperture too far (high f-numbers like f/16 or f/22), light bends around the aperture blades in a phenomenon called diffraction, which softens the image. The diffraction limit tells you the smallest aperture you can use before this softening becomes visible.

How it works

Diffraction is a fundamental wave-optics effect: when light passes through a small opening, it spreads out, forming an Airy disk pattern on the sensor. The Airy disk diameter is approximately 2.44 times the wavelength of light times the f-number (d = 2.44 * lambda * N). When the Airy disk becomes larger than the pixel pitch of the sensor, diffraction softening exceeds the sensor's ability to resolve detail, and you have reached the diffraction limit. Higher-resolution sensors with smaller pixels hit this limit at wider apertures. For example, a 50MP full-frame sensor with ~3.3 micrometer pixel pitch shows diffraction softening around f/8, while a 12MP sensor with ~7 micrometer pixels can be stopped down to f/16 without visible loss. This does not mean you should never exceed the limit — the extra depth of field gained may outweigh the slight softening.

Key factors

Pixel Pitch — The physical size of each pixel on the sensor. Smaller pixels (higher megapixel count for a given sensor size) hit the diffraction limit at wider apertures.

Aperture — Narrower apertures produce larger Airy disks. Past a certain f-number, the Airy disk exceeds the pixel size and detail is lost to diffraction.

Sensor Resolution — Higher megapixel sensors demand more from optics. A 100MP sensor is diffraction-limited at a wider aperture than a 24MP sensor of the same size.

Wavelength of Light — Green light (~550nm) is the standard reference. Shorter wavelengths (blue) diffract less; longer wavelengths (red) diffract more.

Pro Tip

Most lenses reach peak sharpness 2-3 stops down from wide open. For a lens with a maximum aperture of f/2.8, the sweet spot is typically around f/5.6 to f/8.

Pro Tip

If you need both maximum sharpness and great depth of field, consider focus stacking — take multiple shots focused at different distances and merge them in post-processing, rather than stopping down past the diffraction limit.

Pro Tip

Do not be afraid to shoot past the diffraction limit when depth of field is more important than pixel-level sharpness. The softening is subtle and often invisible in normal viewing sizes.

⚡Challengebeginner

You have a 24MP full-frame camera and want the sharpest possible image of a building facade. Your lens goes from f/2.8 to f/22. Which aperture is likely the sharpest?

Hint: Most lenses are sharpest 2-3 stops from wide open, and a 24MP full-frame sensor has relatively large pixels.

Diffraction Limit

Find the sharpest aperture before diffraction softening.

Sensor

Resolution (MP)

Aperture: f/8.0

Pixel Pitch6.00 um

Diffraction Limitf/9.0

Airy Disk Diameter10.74 um

SharpnessSharp — below diffraction limit

Diffraction Limit Calculator

Diffraction Limit

Diffraction Limit