Enter the f-number and the exposure time (shutter speed) into the calculator to determine the exposure value.

## Exposure Value Formula

The following formula is used to calculate an exposure value.

EV = log_{2} (N^{2} / t )

- Where EV is the exposure value
- N is the f-number value
- t is the exposure time/shutter speed (seconds)

## Exposure Value Definition

**What is an exposure value?**

Exposure value is a metric used in photography that represents a combination of f-number and shutter speed such that all combinations that yield the same exposure have the same exposure value.

## Example Problem

How to calculate an exposure value?

**First, determine the f-stop/f-number value.**In this example, the f-number is 3.

**Next, determine the total exposure time.**The exposure time for this example problem is measured to be 1.23 seconds.

**Finally, calculate the exposure value.**Using the formula above, the exposure value is calculated to be:

EV = log_{2}(N^{2}/ t )

EV = log_{2}(3^^{2}/ 1.23 )

EV = 2.871