Equivalent exposure calculator
Metered f/8 at 1/125 s but need a faster shutter? Enter the settings that worked and the ones you want to change — the calculator solves the third side of the exposure triangle and rounds it to a setting your camera actually has.
f/8, 1/125 s at ISO 100 is EV 13.0 (normalised to ISO 100). The equivalent setting is 1/1000 s.
Equivalent exposures at ISO 100
| Aperture | Shutter speed |
|---|---|
| f/1.4 | 1/4000 s |
| f/2 | 1/2000 s |
| f/2.8 | 1/1000 s |
| f/4 | 1/500 s |
| f/5.6 | 1/250 s |
| f/8 | 1/125 s |
| f/11 | 1/60 s |
| f/16 | 1/30 s |
| f/22 | 1/15 s |
Exposure value formula
The calculator converts your metered settings into EV at ISO 100: EV₁₀₀ = log₂(N² ÷ t) − log₂(ISO ÷ 100). Any other combination with the same EV gives the same exposure. Solving for the missing setting: shutter t = N² × 100 ÷ (ISO × 2^EV), aperture N = √(t × ISO × 2^EV ÷ 100) and ISO = 100 × N² ÷ (t × 2^EV). The result is then rounded to the nearest standard 1/3-stop value, and the rounding error is shown so you know whether to nudge exposure compensation.
Typical scene brightness (EV at ISO 100)
| Scene | EV | Example at ISO 100 |
|---|---|---|
| Snow or beach in bright sun | 16 | f/16, 1/250 s |
| Full sun, distinct shadows ("sunny 16") | 15 | f/16, 1/125 s |
| Hazy sun, soft shadows | 14 | f/11, 1/125 s |
| Bright overcast | 13 | f/8, 1/125 s |
| Overcast or open shade | 12 | f/5.6, 1/125 s |
| Bright office or shop interior | 8 | f/2.8, 1/30 s |
| Living room at night | 5 | f/2, 1/8 s |
| Landscape under a full moon | −4 | f/4, 4 min |
Values are approximate starting points — always check the histogram. Learn the theory in the exposure triangle explained, or look up shutter speeds for every ISO and kind of daylight in the sunny 16 rule chart.
More photography calculators
- Depth of field calculatorNear and far limits of sharpness, with a diagram
- Hyperfocal distance calculatorWhere to focus so everything to infinity is sharp
- ND filter calculatorLong exposure times for ND8 to ND64000, with a timer
- Crop factor calculatorEquivalent focal length, aperture and field of view
- 500 rule & NPF calculatorLongest exposure for pinpoint stars
Frequently asked questions
What is the exposure triangle?
Aperture, shutter speed and ISO together decide how bright a photo is. Each can be changed in steps called stops; opening the aperture one stop, using a shutter twice as long or doubling the ISO each make the image twice as bright, so you can trade one for another and keep the same exposure.
What is a stop?
A doubling or halving of light. Shutter speeds and ISO double with each stop (1/250 → 1/125, ISO 100 → 200). Aperture f-numbers multiply by about 1.4 (the square root of 2) per stop: f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16. Most cameras also offer 1/3-stop steps in between.
What is EV (exposure value)?
A single number for a combination of aperture and shutter speed: EV = log₂(N² ÷ t). Normalised to ISO 100 it describes how bright the scene is. Full sun is about EV 15 (the "sunny 16" rule), an overcast day about EV 12, a living room at night about EV 5 and a Milky Way exposure about EV −6.
Do equivalent exposures look the same?
They have the same brightness, but not the same look. A wider aperture gives less depth of field, a slower shutter gives more motion blur and a higher ISO gives more noise. Pick the trade-off that suits the subject.
What is the sunny 16 rule?
In bright sunlight with distinct shadows, a correct exposure is f/16 with a shutter speed of 1 ÷ ISO — for example f/16, 1/100 s at ISO 100. From there you can use this calculator to find any equivalent, such as f/5.6 at 1/800 s.
Does this calculator account for ND filters?
Use the ND filter calculator for that: it multiplies the shutter speed by two for every stop of filter and gives you a Bulb timer for exposures over 30 seconds.