Exposure triangle calculator
Change aperture, shutter speed or ISO and instantly see the stop difference - with the calculator auto-compensating one control so your exposure stays equal to the baseline.
Baseline exposure
Change the other two controls and this one recomputes automatically. Change this one directly and it becomes the new baseline.
Result
Changes vs baseline - equal exposure when the total is 0
Equal-exposure alternates
Standard aperture steps with the shutter (and ISO where marked) chosen so every row matches the baseline exposure. Aperture values are rounded to real thirds stops.
| Aperture | Shutter | ISO | Exposure vs baseline |
|---|
How it works
Three controls set exposure: aperture (how wide the hole is), shutter speed (how long the sensor is exposed) and ISO (how much the signal is amplified). Each is measured in stops - a doubling or halving of light. As long as the three stop-changes sum to zero, the photo stays equally bright:
A stop of aperture is a √2 change in the f-number (f/2.8 → f/4), a stop of shutter is a 2× change in time (1/125 s → 1/60 s), and a stop of ISO is a 2× change in sensitivity (100 → 200).
Example
Baseline f/2.8 · 1/125 s · ISO 100. Stop the aperture to f/5.6 (two stops less light). The calculator doubles the exposure time twice, landing near 1/30 s, or keeps the shutter and raises ISO by two stops to ISO 400 - identical exposure either way.
Why compensate instead of re-meter?
- Stop down for more depth of field and let the shutter or ISO give the light back.
- Freeze motion with a fast shutter, compensating with a wider aperture or higher ISO.
- Keep noise low by preferring aperture/shutter changes over ISO where you can.
Related tools
Need a longer exposure for an ND filter? See the ND filter calculator, or the long exposure calculator. Wondering how slow you can handhold? Check the shutter speed calculator.
Frequently asked questions
What is the exposure triangle?
Aperture, shutter speed and ISO together control how much light reaches the sensor. Changing any one of them by one stop changes the exposure by one stop, so you can always compensate with another control to keep the same brightness.
If I change aperture from f/2.8 to f/4, what shutter do I need?
f/4 lets in one stop less light than f/2.8, so to keep the exposure equal you open the shutter by one stop - for example from 1/125 s to 1/60 s - or double the ISO from 100 to 200.
What is a stop of exposure?
A stop is a doubling or halving of light. One stop longer shutter = 2× the light; one stop narrower aperture (or one stop slower ISO) = half the light. Moving aperture from f/2.8 to f/5.6 closes it by two full stops.
Why does changing aperture by two stops change shutter by four times?
Because each stop doubles or halves the time. A two-stop aperture change (e.g. f/2.8 to f/5.6) lets in 4× less light, so the shutter must run 4× longer (1/125 s → ~1/30 s), or the ISO must be raised 4× (100 → 400).