Photography Calculators

Exposure & light

Exposure Value Calculator

EV is the single number a handheld meter shouts. EV100 is the aperture/shutter pair at ISO 100. EV at your ISO is that value pulled down as you raise sensitivity. Same scene, same light — if two cameras report the same EV at ISO, they should look the same brightness.

Inputs

Units
f/

Taking f-number.

s

Time in seconds. 1/100 is 0.01, 1/250 is 0.004.

Working ISO, not the camera’s dual-gain sweet spot unless that is what you set.

Results

EV at ISO 100
12.64
EV at working ISO
12.64

Lower than EV100 when ISO is above 100 — you needed less light for the same brightness.

Recommended gear

Calculation method

EV at ISO 100 is the base-2 log of f-number squared divided by shutter time in seconds. Raising ISO is equivalent to needing less light, so EV at working ISO subtracts log2 of (ISO/100). Sunny 16 at ISO 100 is about EV 15. A one-stop change in aperture, shutter or ISO moves EV by one.

Exact formula

EV100 = log2(N² / t). EV_ISO = EV100 − log2(ISO/100). Limits: Incident vs reflected, ND, flash contribution and metering pattern omitted; it is the photographic triangle only.

Video people

Cinematographers often talk 180° shutter and T-stops. Convert angle to time with the shutter-angle calculator, then drop that time in here as shutter seconds.

Log profiles

A log picture profile does not change EV. It changes how the file is encoded. Expose for the highlight budget of that profile, then map EV as usual.

Frequently asked questions

Is EV100 what my meter shows?

Many meters show EV at ISO 100 and then you apply ISO. Others show EV at the ISO you dialled. Match the mode; do not mix them.

Why isn’t 1/100 at f/8 ISO 100 equal to 15?

Sunny 16 is f/16 at 1/ISO, which is EV 15. f/8 at 1/100 is two stops more exposure than f/16 at 1/100, so EV 13. The numbers only look ‘off’ if you expected sunny 16.

Does an ND filter change EV?

On the sensor, yes — you need more time or ISO. This calculator does not know about filters. Add the ND stops on the ND calculator, then come back.

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