Exposure calculator: EV, shutter speed, aperture, ISO
The amount of light in the world is predictable and fits a short EV scale, where each unit is exactly one stop. Knowing the scene's brightness, you can work out exposure ahead of time, at home, and tell whether the shot will work at all.
Your combination
Reverse calculation from brightness
Set the scene's brightness — the calculator finds the missing parameter for your combination.
A camera's meter reads reflected light and gets fooled by unusual scenes: it turns snow gray, and a black car gray too. Knowing the expected EV is a way to catch that mistake.
How it's calculated
- EV is a scale where each unit equals exactly one stop. The pair “aperture plus shutter speed” sets the EV uniquely.
- Sensitivity is factored in separately, normalized to ISO 100 — that's what makes values from different cameras comparable.
- Knowing the scene's EV, the missing parameter — shutter speed, aperture, or ISO — is found by working backward.
Example: f/5.6 at 1/125 and ISO 100 is EV 11.9. If the scene is actually EV 15, at the same aperture and ISO the shutter speed needed is about 1/1045.
EV = log₂(N²/t) at ISO 100; at other sensitivities, EV₁₀₀ = log₂(N²/t) − log₂(ISO/100). The “sunny 16” rule: a clear day ≈ EV 15, i.e. f/16 at a shutter speed of 1/ISO.
This is an estimate
Verify final values against current standards, the project design, and equipment nameplates.