Exposure Stops Calculator
Compare two aperture, shutter speed, or ISO settings in stops and see the net effect on image brightness.
Aperture and shutter stops are positive when they let in less light (smaller aperture opening, faster shutter). ISO stops are positive when they add more sensitivity, and therefore more apparent light.
How it works
A stop is a doubling or halving of light. Aperture, shutter speed, and ISO each measure stops differently, and this tool converts all three to the same scale so you can see how a change in one balances a change in another. Aperture stops come from the ratio of the two f-numbers: going from f/2.8 to f/5.6 is 2 stops, meaning the sensor receives a quarter of the light, even though the numbers themselves don't look like they doubled. Shutter stops work off the ratio of the two speeds: 1/100 s to 1/400 s is also 2 stops, since the shutter is open a quarter as long.
ISO works the opposite direction from the other two. Raising ISO from 100 to 400 is 2 stops of MORE apparent light, because the sensor is amplifying the same physical light more aggressively, not because more light actually hit it. That's why the net brightness verdict subtracts the light lost to aperture and shutter changes from the gain added by ISO. Worked example: stopping down 2 stops (f/2.8 to f/5.6) loses 2 stops of light, and raising ISO from 100 to 400 gains 2 stops back, so the two changes cancel out and the final image comes out at the same overall brightness as the starting exposure.
FAQ
Why would I want to know this instead of just checking my light meter?
Your camera's meter tells you if an exposure is balanced right now, but this tool helps you plan a trade before you make it, like knowing exactly how much to raise ISO if you need a faster shutter speed to freeze motion in low light.
Is 1 stop always the same amount of visible brightness change?
Yes, that's the whole point of measuring in stops rather than raw f-numbers or shutter fractions. One stop is always a doubling or halving of light reaching the sensor, regardless of which of the three controls produced it.
Why do smaller f-numbers mean more light and bigger numbers mean less?
The f-number is a ratio of focal length to the aperture opening's diameter, so a small number like f/1.8 describes a relatively wide opening, and a large number like f/16 describes a narrow one. Wider openings let in more light.
Does raising ISO actually add noise, or is that a separate issue?
It's related but separate. Higher ISO amplifies both the signal and the sensor's background noise, so images get grainier as ISO climbs, especially past 1600 or 3200 on most consumer cameras. This tool only calculates the brightness math, not the noise tradeoff.
For the fundamentals behind these three controls, see the exposure triangle explained, exposure compensation, and what ISO actually does.