EV at ISO 100 from f-number, shutter time in seconds, and ISO.
| EV100 | – |
Use this calculator to get the APEX exposure value of a camera setting, referred to ISO 100. Enter the f-number, the shutter time in seconds, and the ISO.
EV100 = log2(N² / t) − log2(ISO / 100). f/8 at 1/125 s (0.008 s) and ISO 100 is EV 13. Doubling ISO subtracts one stop from EV100 in this convention.
Sunny-16 is a lighting rule of thumb, not this algebra. The calculator does not meter a scene; it only converts the three exposure parameters.
f-number: Aperture N, for example 8 for f/8.
Shutter (s): Exposure time in seconds, for example 0.008 for 1/125.
ISO: Sensor ISO, not zero.
EV100: Exposure value referred to ISO 100.
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