Numerical Aperture to Equivalent F/stop

This calculator helps you convert Numerical Aperture (NA) values into equivalent f-stop numbers, commonly used in photography and microscopy to represent the light-gathering ability of a lens or optical system.

What is NA?

The Numerical Aperture (NA) of an optical system is a dimensionless number that characterizes the range of angles over which the system can accept or emit light. It’s commonly used in microscopy to describe how much light a lens can gather.

What is f-stop?

The f-stop (also called the f-number) is a measure of the aperture size in photography, representing the ratio of the lens’s focal length to the diameter of the entrance pupil. A lower f-stop allows more light to enter, while a higher f-stop reduces the amount of light entering the lens.

NA to f-stop conversion can be made using this simple formula:

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f/stop_{Equivalent}=Objective\,Magnification*\frac{1}{2*NA}
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