What is exposure value (EV)?

Exposure value is a single number describing all aperture and shutter combinations that give the same exposure. EV = log2(N² / t), where N is the f-number and t is the shutter time in seconds.

What is the difference between EV and EV100?

EV100 normalises exposure value to ISO 100 so light levels can be compared regardless of ISO. EV100 = EV minus log2(ISO / 100).

How do I enter shutter speed as a decimal?

Divide one by the denominator. 1/125 s becomes 0.008, 1/250 s becomes 0.004 and 1/1000 s becomes 0.001. Whole-second exposures are entered directly, such as 2 for a two-second exposure.

What does one stop of EV mean?

Each whole EV step doubles or halves the light. Increasing EV by 1 means half as much light reaches the sensor (a faster shutter or smaller aperture); decreasing EV by 1 doubles it.

What is a typical EV for daylight?

Bright sunlight is roughly EV100 15, an overcast day around EV100 12, indoors under normal lighting around EV100 7, and a dim night scene below EV100 3. EV100 lets you compare these regardless of the ISO you shoot at.

Why use EV100 instead of plain EV?

Plain EV depends on your ISO, so the same scene gives different numbers at ISO 100 and ISO 800. EV100 normalises everything to ISO 100, giving a single value for the scene's brightness that you can compare or look up against light-meter charts.

Exposure Value (EV) Calculator

Q: Is anything uploaded?

No — all calculations happen in your browser and nothing is sent anywhere.

Exposure value calculator

Exposure value (EV) is a single number that captures a whole family of equivalent exposures: every aperture and shutter combination giving the same brightness shares one EV. It is the language light meters and the “sunny 16” rule speak in. Enter your aperture, shutter speed and ISO, and this tool returns the EV at your ISO plus the EV100 value referenced to ISO 100.

How it works

The calculator uses the standard definitions. Exposure value from aperture and shutter is EV = log₂(N² / t), where N is the f-number and t is the shutter time in seconds. To compare scenes independent of sensitivity it then corrects for ISO: EV100 = EV − log₂(ISO / 100). Each whole step represents one stop — a doubling or halving of light.

Example

At f/8, 1/125 s (0.008 s), ISO 100:

EV = log₂(8² / 0.008) = log₂(64 / 0.008) = log₂(8000) ≈ 12.97.

Because ISO is 100, the correction is zero, so EV100 ≈ 12.97 too — consistent with a typical overcast daytime scene.

Aperture	Shutter	ISO	EV ≈	EV100 ≈
f/8	1/125 s	100	12.97	12.97
f/8	1/125 s	800	12.97	9.97

All calculations happen in your browser and nothing is sent anywhere.