Estimate the Airy disk size and whether diffraction softens your image.
Diffraction spreads each point of light into an Airy disk whose size grows with the f-number, softening detail when it exceeds the pixel pitch. Stopping down too far trades depth of field for diffraction blur, so there is a sweet spot aperture for maximum resolution.
Aperture Diffraction Limit
Airy disk = 2.44 x wavelength (550nm) x f-number
Airy disk = 2.44 x wavelength (550nm) x f-number Diffraction spreads each point of light into an Airy disk whose size grows with the f-number, softening detail when it exceeds the pixel pitch.
Stopping down too far trades depth of field for diffraction blur, so there is a sweet spot aperture for maximum resolution.
This calculator takes 2 inputs: Aperture (f-number), Sensor pixel pitch. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.