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Conversion of f/# and NA

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Optics index
Conversion of f/# and NA diagram
calc
The f-number (f/#) and numerical aperture (NA) are calculated as defined. This calc converts between them, and also gives the angle (α) of collection for the lens. The f-number is defined in air, but for the NA, refractive index is taken into account if necessary.
f/#
NA
Refractive index (n)

f/#
NA
Angle α
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notes
Fill in either the f/# or the NA. The calc will provide the conversion as well as give the angle α.
If you fill in both inputs, then both will be converted.