The filter decides which wavelengths of light reach your sensor, and the wavelength decides how large the Airy disk is at each ƒ-stop. That’s why the diffraction calculator asks for your filter as well as your camera. This page lists the wavelengths the calculator uses for each filter.

Filters and the wavelengths they pass

Filters
Filter Wavelengths used (nm)
Full spectrum 350, 400, 470, 550, 590, 665, 720, 780, 830, 930, 1000
Hot mirror or UV/IR cut 470, 550, 590, 665, 720
470 nm high-pass 470, 550, 590, 665, 720, 780, 830, 930, 1000
550 nm high-pass 550, 590, 665, 720, 780, 830, 930, 1000
590 nm high-pass 590, 665, 720, 780, 830, 930, 1000
665 nm high-pass 665, 720, 780, 830, 930, 1000
720 nm high-pass 720, 780, 830, 930, 1000
780 nm high-pass 780, 830, 930, 1000
830 nm high-pass 830, 930, 1000
930 nm high-pass 930, 1000
1000 nm high-pass 1000
IR Chrome 470, 720, 780, 830, 930, 1000
UV Bandpass 350, 400
  • Full spectrum is a converted camera with no filter on the lens. It captures ultraviolet, visible, and infrared light, so the calculator supports these wavelengths.
  • Hot mirror or UV/IR cut is an unconverted camera, or a full spectrum camera with a UV/IR cut filter. It captures visible light only.
  • High-pass filters (470 nm to 1000 nm) block light below their rating and pass everything above it. The transition is sharp with quality filters and gradual with lower quality filters.
  • IR Chrome passes a band of blue light plus infrared from 720 nm and up.
  • UV Bandpass passes ultraviolet light only.

Why the longest wavelength sets the limit

The Airy disk grows with wavelength: at the same ƒ-stop, 1000 nm infrared light makes a disk almost three times as wide as 350 nm ultraviolet light. The calculator rates a filter by the worst wavelength it passes, so the longest wavelength sets the sharpest usable ƒ-stop.

That’s why every infrared high-pass filter, IR Chrome, and full spectrum give the same Safe, Caution, and Avoid ƒ-stops for a camera: they all pass 1000 nm. Visible light alone (hot mirror) can stop down further before diffraction shows, and UV bandpass further still. See how the diffraction ratio is calculated for the formula.

Wavelengths the calculator samples

Light is continuous, so the calculator compares 11 sample wavelengths from 350 to 1000 nm. They are the columns of its table:

  • Ultraviolet: 350 and 400 nm
  • Visible light: 470, 550, 590, 665 and 720 nm
  • Infrared: 780, 830, 930 and 1000 nm

Each visible and infrared sample matches a high-pass filter rating, so every high-pass filter’s cut-on point is one of the columns.