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Exposure Value Calculator

Work out exposure value instantly with clear inputs, formula shown and shareable results.

About Exposure Value Calculator

Exposure value is the base-two logarithm of the aperture squared divided by the shutter time, and subtracting log2 of ISO over 100 refers it to the ISO 100 scale. EV is a single number for a whole exposure, which is why one EV equals one stop and any aperture and shutter pair on the same EV gives the same brightness.

Formulas

Exposure value

EV = log2(aperture^2 / shutter time in seconds)

ISO reference

EV at ISO 100 = EV - log2(ISO / 100)

Worked example

With the default values below, Exposure Value Calculator returns Exposure value at this ISO of 11.937. Change any input above and every figure here is recalculated in your browser.

Inputs used

Apertureminimum 0.5 f
5.6 f
Shutter speedminimum 0 s
0.008 s
ISOminimum 1
200

Results

Exposure value at this ISO
11.937 EV
Exposure value referred to ISO 100
10.937 EV
Approximate scene luminance
245.0000 cd/m2
Shutter speed as a fraction
1/125

Step by step

  1. 1Values used
  2. 2Exposure value
  3. 3ISO reference
  4. 4Exposure value at this ISO= 11.937 EV
  5. 5Exposure value referred to ISO 100= 10.937 EV
  6. 6Approximate scene luminance= 245.0000 cd/m2
  7. 7Shutter speed as a fraction= 1/125

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Exposure Value figure worked out?

EV = log2(aperture^2 / shutter time in seconds). Exposure value is the base-two logarithm of the aperture squared divided by the shutter time, and subtracting log2 of ISO over 100 refers it to the ISO 100 scale.

Why does this matter?

EV is a single number for a whole exposure, which is why one EV equals one stop and any aperture and shutter pair on the same EV gives the same brightness.

What do I need to enter?

Enter aperture, shutter speed, iso. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.

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