Lens Diffraction Calculator
Find the diffraction-limited aperture for your sensor to maintain optimal sharpness. Enter values for instant results with step-by-step formulas.
Formula
Airy Disk = 2.44 x Wavelength x f-number | Diffraction Limit = 2 x Pixel Pitch / (2.44 x Wavelength)
The Airy disk diameter determines the smallest detail a lens can resolve at a given aperture. When the Airy disk exceeds twice the pixel pitch (Nyquist limit), the sensor cannot fully resolve the diffraction pattern, and effective resolution begins to decrease. The diffraction-limited f-number is the aperture at which this threshold is reached.
Worked Examples
Example 1: 24MP Full Frame at f/11
Problem: A photographer with a 24-megapixel full-frame camera (36x24mm sensor) wants to know if shooting at f/11 causes diffraction softening.
Solution: Pixel pitch = 36mm / sqrt(24M x 1.5) = 36mm / 6000 = 6.0 micrometers\nAiry disk at f/11 = 2.44 x 0.00055mm x 11 = 0.01477mm = 14.77 micrometers\nDiffraction limit = 2 x pixel pitch / (2.44 x wavelength) = 12 / (2.44 x 0.00055) = f/8.9\nAt f/11, Airy disk (14.77um) > 2x pixel pitch (12um)\nResolution loss: approximately 15-20%\nEffective resolution drops from 24MP to approximately 16MP
Result: Diffraction limited at f/11 | Limit: f/8.9 | Effective MP: ~16MP
Example 2: 45MP Full Frame Landscape Aperture
Problem: A landscape photographer with a 45-megapixel full-frame camera needs to determine the sharpest aperture for maximum resolution.
Solution: Pixel pitch = 36mm / sqrt(45M x 1.5) = 36mm / 8216 = 4.38 micrometers\nDiffraction limit = 2 x 4.38 / (2.44 x 0.55) = 8.76 / 1.342 = f/6.5\nOptimal range: f/4 to f/6.5 for maximum resolution\nAt f/8: Airy disk = 10.7um vs 8.76um limit = ~17% resolution loss\nAt f/11: Airy disk = 14.7um = ~40% resolution loss\nAt f/16: Airy disk = 21.5um = ~68% resolution loss
Result: Diffraction limit: f/6.5 | Optimal: f/4-f/6.5 | f/8 loses ~17%
Frequently Asked Questions
What is lens diffraction and how does it affect image sharpness?
Lens diffraction is a physical phenomenon where light waves bend as they pass through a small aperture opening, causing the light to spread rather than focus to a sharp point. Every lens produces a small diffraction pattern called an Airy disk at each point in the image. At wider apertures like f/2.8 or f/4, the Airy disk is smaller than the pixel size on your sensor, so diffraction has no visible effect. As you stop down to smaller apertures like f/16 or f/22, the Airy disk grows larger and eventually exceeds the pixel pitch, causing light from one point to bleed into neighboring pixels. This results in a softening of the image that cannot be corrected in post-processing because the fine detail information has been physically lost. Understanding diffraction helps you choose the optimal aperture for maximum sharpness.
At what aperture does diffraction start affecting my camera?
The diffraction-limited aperture depends primarily on your sensor pixel pitch. For common cameras: a 12MP full-frame camera becomes diffraction limited around f/14 to f/16, a 24MP full-frame around f/10 to f/11, a 45MP full-frame around f/7 to f/8, a 24MP APS-C around f/7 to f/8, and a 20MP Micro Four Thirds around f/6 to f/7. These values assume green light at 550nm wavelength. Shorter wavelengths like blue produce smaller Airy disks, while longer wavelengths like red produce larger ones. The practical impact varies because diffraction onset is gradual. At one stop past the diffraction limit, resolution loss is typically 10 to 15 percent, which may be acceptable for many applications. At two stops past, the loss reaches 30 to 40 percent and becomes quite visible even in moderate-sized prints.
Should I always avoid apertures past the diffraction limit?
No, the diffraction limit should inform your choices but not dictate them absolutely. There are many valid reasons to shoot past the diffraction-limited aperture. Landscape photography often requires f/16 or f/22 for sufficient depth of field, and the sharpness gained from having the entire scene in focus outweighs the resolution lost to diffraction. Macro photography frequently requires f/16 to f/22 because depth of field at close focusing distances is extremely shallow. Architectural photography benefits from small apertures for front-to-back sharpness. The key is understanding the tradeoff: you are sacrificing some resolution for greater depth of field. For images that will be viewed at normal sizes on screens or in moderate prints, the diffraction softening at f/16 is rarely noticeable. For large prints or heavy cropping, staying near the diffraction limit becomes more important.
How does sensor size affect diffraction sensitivity?
Sensor size affects diffraction sensitivity indirectly through its relationship with pixel pitch. A smaller sensor with the same megapixel count has smaller pixels and therefore becomes diffraction limited at wider apertures. A 24MP Micro Four Thirds sensor has roughly 3.3-micrometer pixels and hits the diffraction limit around f/5.6, while a 24MP full-frame sensor has 6-micrometer pixels and reaches the limit around f/11. However, when comparing images at the same final output size, smaller sensors require less magnification per pixel, partially offsetting the diffraction penalty. The net effect is that smaller sensors are still more practically limited by diffraction but not as severely as raw pixel-level analysis suggests. Medium format sensors with large pixel pitches enjoy the most headroom, with some 50MP medium format cameras staying diffraction-free up to f/14 or beyond.
Can I correct diffraction softening in post-processing?
Diffraction softening cannot be fully corrected in post-processing because the fine detail information is physically lost when the Airy disk spreads light across multiple pixels. However, moderate sharpening and deconvolution algorithms can partially compensate for mild diffraction effects. Software like Topaz Sharpen AI, DxO PhotoLab, and Adobe Camera Raw can recover some apparent sharpness from diffraction-softened images. These tools work best when the diffraction is mild, up to about one stop past the limit. Beyond that, sharpening creates artifacts rather than recovering genuine detail. Some cameras apply in-camera diffraction correction for JPEG output, using the known lens aperture to apply appropriate deconvolution. For optimal results, capture the sharpest possible image in camera and use software corrections only as a supplement, not a replacement for proper aperture selection.
How does wavelength of light affect diffraction calculations?
The wavelength of light directly affects the size of the Airy disk according to the formula: diameter = 2.44 times wavelength times f-number. Green light at 550nm is typically used for calculations because human vision is most sensitive to green and most camera sensors have the highest green pixel count in their Bayer pattern. Blue light at 450nm produces a smaller Airy disk (approximately 18% smaller than green), meaning blue channels in your image remain sharp at slightly smaller apertures. Red light at 650nm produces a larger Airy disk (approximately 18% larger than green), making the red channel more susceptible to diffraction. In practice, this means images with predominantly blue subjects like sky and water retain sharpness slightly better at small apertures than images with predominantly red subjects. Infrared photography at 800nm or beyond is especially affected by diffraction.