Exposure Triangle Calculator
Aperture, shutter speed, and ISO together set how bright a photograph is, and each one can be measured in stops on a single scale. This calculator computes the exposure value (EV) from your f-number and shutter speed, then shows how aperture, shutter, and ISO each contribute in stops. Understanding these numbers is what lets you trade one setting for another, opening the aperture while shortening the shutter, for instance, to change depth of field or freeze motion without altering overall brightness.
Exposure triangle formula
EV (ISO 100) = log2( N^2 / t )
where N = f-number, t = shutter time in seconds
ISO stops = log2( ISO / 100 )
adjusted EV = EV (ISO 100) - ISO stops
aperture stops vs f/1.0 = log2( N^2 ) = 2 * log2(N)
This follows the APEX (Additive System of Photographic Exposure) definition of exposure value. Raising ISO lowers the EV needed for the same brightness, so the adjusted EV subtracts the ISO stops.
Exposure facts
- One stop doubles or halves the light reaching the sensor.
- Common full f-stops are 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, each a stop apart.
- Halving the shutter time is one stop less exposure; doubling it is one stop more.
- Doubling ISO is one stop more sensitivity but usually adds noise.
- To hold exposure constant, offset a change in one setting with an equal opposite change in another.
Exposure triangle: frequently asked questions
What is the exposure triangle?
The exposure triangle is the relationship between aperture (f-number), shutter speed, and ISO. Each controls how much light reaches the sensor or how it is amplified. Changing one by a full stop doubles or halves the light, so a change in one can be balanced by an opposite change in another to keep brightness constant.
How is exposure value (EV) calculated?
Exposure value at ISO 100 is defined as EV = log2(N squared / t), where N is the f-number and t is the shutter speed in seconds. Higher EV means a brighter scene needs less exposure. This calculator computes EV from your aperture and shutter speed and adjusts for ISO.
What is a stop in photography?
A stop is a doubling or halving of light. Going from f/4 to f/5.6 is one stop less light; halving shutter time from 1/100 to 1/200 is one stop less; doubling ISO from 100 to 200 is one stop more sensitivity. Stops let you compare aperture, shutter, and ISO on a single scale.
How do I keep the same exposure when I change a setting?
If you change one setting by a number of stops, change another by the same number of stops in the opposite direction. For example, opening the aperture by one stop (more light) and halving the shutter time by one stop (less light) leaves total exposure unchanged while altering depth of field or motion blur.
Why does ISO appear in the calculation?
EV is defined at a reference of ISO 100. Raising ISO amplifies the signal, so the camera needs less light for the same brightness. This calculator expresses the ISO change in stops relative to 100 (log2 of ISO divided by 100) and reports it alongside the aperture and shutter contributions.
Official sources
- International Organization for Standardization: ISO 12232 photographic sensitivity.
- National Institute of Standards and Technology (NIST): Units and measurement reference.
Reviewed by the CalculatorHub team, edited by James Graham, 16 June 2026. See our methodology.