๐ท Shutter Speed Calculator
B is the slower (brighter) shutter speed
* Enter a fraction like "1/125", or a number of seconds like "2" or "0.5".
Enter two shutter speeds โ as a fraction like "1/125" or a number of seconds โ and see the difference between them in stops (EV). Useful for adjusting exposure compensation or manual camera settings, so you know exactly how much brighter or darker a change will make your shot.
How to use
- Enter the two shutter speeds you want to compare, as a fraction like "1/125" or a number of seconds like "2".
- The equivalent value in milliseconds for each, and the stop (EV) difference between them, are shown automatically.
How the calculation works
Photographic exposure is measured in stops (EV). One stop is a doubling or halving of light. Shutter speed is how long light is let in, so doubling the time doubles the light โ one stop brighter. The number of stops between two shutter speeds is the base-2 logarithm of the longer time divided by the shorter. For 1/60 s and 1/125 s: (1/60) รท (1/125) โ 2.08, and logโ(2.08) โ 1.06, so very nearly one stop. The speeds a camera displays (1/30, 1/60, 1/125, 1/250โฆ) are not exact doublings; they are rounded to memorable values. That is why the arithmetic produces fractions like 1.06 stops, even though the camera treats the step as exactly one.
Worked example
Changing from 1/125 s to 1/30 s 1. Time ratio: (1/30) รท (1/125) = 125 รท 30 โ 4.17 2. Stops: logโ(4.17) โ 2.06 About two stops brighter. To get the same brightness indoors without risking motion blur, you could instead leave the shutter alone and raise ISO by two stops (say ISO 400 โ 1600). 1 s versus 1/8 s is logโ(8) = 3, exactly three stops.
Things to be aware of
- Displayed speeds are rounded, so fractional results still correspond to whole-stop settings in practice.
- Slower shutter speeds brighten the image but make camera shake and subject blur more likely.
- This tool does not calculate stops for aperture (f-number) or ISO.
- Exposure compensation of +1 or โ1 is also a one-stop change.
FAQ
What does "stops (EV)" mean?
A stop (or EV, exposure value) is a photography unit where 1 stop means doubling or halving the amount of light. Slowing the shutter speed by 1 stop lets in twice as much light.
Does this support formats other than "1/125"?
Yes โ besides fraction notation like "1/125", you can also enter a number of seconds like "2" or "0.5" (decimals allowed).
Can this calculate stops for aperture (f-stop) or ISO too?
No โ this tool is dedicated to calculating the stop difference between shutter speeds only.