Camera Exposure Triangle Calculator
Work the exposure triangle: enter aperture, shutter speed, and ISO to get the EV, or solve for the aperture or shutter that hits a target EV.
Result
- Aperturef/2.8
- Shutter1/125 s (0.008 s)
- ISO100
- EV (at ISO 100)9.94
- Scene EV correctly exposed at this ISO9.94
Step-by-step
- EV = log₂(N² ÷ t) = log₂(2.8² ÷ 0.008) = log₂(980) = 9.94 (at ISO 100).
- ISO 100 shifts metering by log₂(ISO/100) = 0.00 EV, so this exposes a scene of EV 9.94.
How to use this calculator
- Choose what to solve for: EV from your settings, or the aperture/shutter for a target EV.
- Enter aperture as the f-number (e.g. 2.8) and shutter as seconds (1/125 s = 0.008).
- Set the ISO; EV is referenced to ISO 100 and the tool shows the ISO shift.
- In solve modes, set the target EV and read the required setting.
About this calculator
The exposure triangle describes how a photograph's brightness depends on three settings: aperture (the f-number, controlling how much light the lens lets in), shutter speed (how long the sensor is exposed), and ISO (the sensor's sensitivity). They trade off against one another — open the aperture one stop and you can halve the exposure time for the same brightness. This calculator works the triangle two ways. In EV mode it reads out the exposure value of a given aperture and shutter, EV = log₂(N²/t), defined at ISO 100, and shows what scene brightness that exposes correctly at your chosen ISO. In the solve modes it back-calculates the aperture or shutter speed needed to hit a target EV. Each whole number of EV is one "stop" — a doubling or halving of light.
How it works — the formula
EV = log₂(N² ÷ t) (at ISO 100)
Aperture: N = √(t × 2^EV_eff)
Shutter: t = N² ÷ 2^EV_eff
EV_eff = target EV + log₂(ISO ÷ 100)Exposure value is the base-2 logarithm of the aperture-area-to-time ratio. Solving for one setting inverts the relation; ISO shifts the effective EV the sensor needs by one stop per doubling.
Worked examples
- Inputs:
- mode=ev, aperture=2.8, shutter=0.008, iso=100
- Output:
- log₂(7.84 ÷ 0.008) = EV 9.94
- Inputs:
- mode=ev, aperture=8, shutter=0.004
- Output:
- log₂(64 ÷ 0.004) = EV 13.97
- Inputs:
- mode=aperture, shutter=0.002, targetEv=12, iso=100
- Output:
- √(0.002 × 4096) = f/2.9
Limitations
- EV is defined at ISO 100; the tool shows the ISO shift but EV itself excludes ISO.
- Ignores lens light-transmission (T-stop vs f-stop) and reciprocity failure.
- Solved values are exact numbers, not snapped to standard stop increments.
A metering aid; final exposure also depends on metering mode and scene reflectance.