What is numerical aperture?

 

Numerical aperture (NA) is defined by the angular range over which a system can accept or emit light. It is defined by the formula NA=nā‹…sinā”(Ī±/2), where n is the refractive index of the medium and Ī± is the full opening angle of the light cone. In air n=1.

Angle to NA to f-number to steradian

Convert angle, numerical aperture, f-number, and steradian into each other. You can provide any of the values, and the other three values will be calculated.