Exposure value (EV) calculator
Turn an aperture, shutter speed and ISO into an exposure value, compare it with typical lighting, and list every combination that gives the same exposure.
Exposure value
EV 13.0
log₂(8² ÷ 1/125)
At ISO 100 (scene brightness)
EV100 13.0
Equivalent exposures
| Aperture | Exact time | Camera setting |
|---|---|---|
The formula
Exposure value combines aperture and shutter speed into one number: EV = log₂(N² ÷ t), where N is the f-number and t the exposure time in seconds. EV 0 is f/1 for one second, and each step of 1 is one stop: half the light. f/16 at 1/125 s works out at EV 15, the classic sunny-day exposure. Because EV only describes the camera settings, the same EV can come from f/8 at 1/500 or f/4 at 1/2000.
ISO and scene brightness
To compare with light-level tables, the settings are converted to ISO 100: EV100 = EV − log₂(ISO ÷ 100). Going the other way, a scene's EV at ISO 400 is its EV100 plus 2, so you need two stops less light from aperture and shutter. The lighting list uses typical ISO 100 values from the ANSI exposure guides, as tabulated on Wikipedia: full sun EV 15, heavy overcast EV 12, just after sunset around EV 10. Treat them as a starting point and check your histogram.
Equivalent exposures
The table keeps the exposure constant and lists each full-stop aperture with its shutter time, at any ISO you pick. Exact times use the true values behind the rounded camera labels (f/5.6 is really 5.66), then show the nearest third-stop setting.
Sources
- Wikipedia, Exposure value: the definition, the ISO adjustment and table 2 of typical lighting conditions (from ANSI PH2.7-1973 and PH2.7-1986).
- Wikipedia, Sunny 16 rule.
Questions
Is a higher EV brighter?
No, the opposite. A higher EV means less light reaches the sensor at those settings, which suits a brighter scene. Bright sun is around EV 15 at ISO 100; a night street is around EV 7.
Why does my camera's meter disagree with the scene table?
The table describes typical scenes with front lighting. Backlight, snow, dark subjects and the meter mode all shift the right exposure.
What is the sunny 16 rule?
In bright sun, use f/16 with a shutter time of one over the ISO, such as 1/100 s at ISO 100. That is about EV 15, the value for full sun in the table.