Exposure and EV Calculator
Enter any ISO, aperture, and shutter. Get the exposure value and every equivalent setting that gives you the same negative.
Exposure value (EV) collapses three settings into one number. The formula meters use is EV at ISO 100 equals the base-2 logarithm of the aperture squared divided by the shutter time, minus the base-2 logarithm of the ISO over 100. In plain terms: a smaller aperture or a faster shutter raises the EV, and faster film lowers the EV the scene needs. One full stop in any direction moves the EV by exactly one.
Once you know the EV, every aperture and shutter pair that holds the same exposure is an equivalent exposure. Photographers swap between them to control depth of field and motion blur without changing how bright the negative comes out. The table below lists those pairs at full stops, and it includes the Sunny 16 starting point for your film so you have a sanity check for a bright sunny day.
Equivalent settings
| Aperture | Shutter |
|---|
How to use it
Type in the ISO of your film, the f-number you want, and a shutter time. Shutter speeds shorter than a second are written as fractions like 1/125; times of a second or longer are written as plain numbers like 2 or 0.5. The EV updates as you type, and the table shows you the alternate settings that hold the same exposure so you can pick the one that suits the shot.
Frequently asked
What is EV?
Exposure value is a single number that captures how much light an exposure lets in. Every combination of aperture and shutter that gives the same exposure shares one EV. Stopping down one full stop or halving the shutter both raise the EV by one.
What does EV at ISO 100 mean?
Light meters quote EV referenced to ISO 100 so the number describes the scene brightness, not your film speed. Once you pick a film, the actual aperture and shutter you set shift with the ISO, but the scene's EV100 stays the same.
What are equivalent exposures?
Different aperture and shutter pairs that produce the same exposure. f/8 at 1/250 and f/11 at 1/125 let in identical light. You trade depth of field against motion blur while the brightness of the negative stays fixed.
Zone Light Meter for Android does this from a live reading: point it at the scene, and it gives you the EV and the full ladder of equivalent settings for whatever film you have loaded.