Stops of Light Calculator

About this calculator

In photography, a stop of light represents a doubling or halving of exposure. This calculator finds the difference in stops between two exposure values as Δstops = log₂(E2/E1) — so if one setting lets in exactly twice the light of another, that's a 1-stop difference; four times the light is 2 stops, since each additional stop doubles again (2ⁿ brightness ratio for n stops).

Stops give photographers a single unit that works across aperture, shutter speed, and ISO simultaneously — opening the aperture one stop (say f/4 to f/2.8), halving the shutter speed (1/250s to 1/125s), or doubling the ISO (400 to 800) all add exactly one stop of exposure, and any combination can be swapped to keep total exposure constant. Photographers, cinematographers, and lighting technicians use stop differences to match exposure between two camera settings, calculate flash power adjustments, or convert a light meter reading into a usable aperture/shutter combination.