Exposure Calculator
Work out the exposure value of any aperture, shutter speed and ISO, find the equivalent setting when you change one, or start from a sunny 16 style scene table.
The interactive tool loads here when JavaScript runs.
About this toolWhat is the Exposure Calculator?
This exposure calculator handles the arithmetic of the exposure triangle. Enter the aperture, shutter speed and ISO your meter gave you and it reports the exposure value, then tells you the shutter speed, aperture or ISO that gives the same exposure after you change one of the others, rounded to the nearest setting your camera actually offers.
The second mode starts from the light. Pick a scene such as full sun, heavy overcast, a lit street at night or the Milky Way, choose your ISO and either the aperture or the shutter speed, and it suggests the other. A table lists every equivalent pair from f/1.4 to f/22 so you can choose between freezing motion and gaining depth of field.
- EV and EV100 from aperture, shutter speed and ISO
- Solve for shutter, aperture or ISO with nearest third-stop setting
- Scene light table from bright snow to the Milky Way core
- Equivalent exposure table from f/1.4 to f/22
- Accepts 1/250, 0.5, 2 and 2m30s style shutter times
- Copy results and shareable links
How to use the Exposure Calculator
- In Equivalent exposure mode, enter the metered aperture, shutter speed (1/125, 0.5 or 2) and ISO.
- Choose what to solve: a new shutter speed, aperture or ISO.
- Enter the two settings you want to fix. The answer and the nearest camera setting appear at once.
- Or switch to Settings from the scene, pick the lighting or type an EV from a hand meter, set the ISO and the aperture or shutter you want, and read the other.
- Use the table to compare every aperture at the same exposure.
Worked examples
Opening up for a blurred background
Input
Metered f/8, 1/125 s, ISO 100; new aperture f/2.8, same ISO
Output
About 1/1020 s; nearest setting 1/1000
f/8 to f/2.8 is three stops more light, so the shutter must be three stops faster.
Raising ISO to freeze action
Input
Metered f/8, 1/125 s, ISO 100; keep f/8, want 1/1000 s
Output
ISO 800
Three stops faster shutter needs three stops more sensitivity: 100, 200, 400, 800.
Sunny 16 at ISO 400
Input
Scene: full sun, EV100 15; ISO 400; aperture f/16
Output
About 1/512 s; nearest 1/500
The rule says 1/ISO, which is 1/400 s; the table value of EV 15 is a third of a stop brighter than sunny 16 assumes.
Background and insight
Exposure value collapses aperture and shutter time into one number: EV = log₂(N²/t), where N is the f-number and t the time in seconds. f/1 at 1 second is EV 0, and each step of 1 EV halves the light reaching the sensor. Every combination with the same EV gives the same exposure: f/8 at 1/125 s, f/5.6 at 1/250 s and f/11 at 1/60 s are all about EV 13.
ISO shifts which EV a scene needs. Light levels are quoted as EV at ISO 100 (EV100), and at another ISO S the camera setting becomes EV100 + log₂(S/100), so ISO 400 adds two stops. The scene table in the tool uses the values in the Wikipedia Exposure value article, which follow the exposure tables of ANSI PH2.7: about EV 15 for a sunlit scene with distinct shadows, 12 for heavy overcast or open shade, 8 for a bright street at night and around −10 for the Milky Way core.
The sunny 16 rule is the same table in words: in bright sun, set f/16 and a shutter speed of 1/ISO. At ISO 100 that is f/16 at 1/100 s, EV100 14.6, within half a stop of the EV 15 in the table. Camera dials step in third stops, so the tool reports the exact answer and the nearest marked setting with the error in stops.
Common use cases
Changing one setting without re-metering
Open the aperture, add an ND filter or raise the ISO and keep the same exposure.
Manual cameras and film
Get a sensible starting exposure from the scene when the camera has no meter or the battery is flat.
Flash and studio work
Translate a hand-meter reading into the combination you want for depth of field.
Night and astro planning
Estimate the shutter time for a street scene, an aurora or the Milky Way before you go out.
Teaching the exposure triangle
Show students how stops of aperture, shutter and ISO trade one for one.
Tips and limitations
- One stop of aperture is a factor of √2 in f-number (f/4 to f/5.6), while one stop of shutter or ISO is a factor of 2.
- Scene values assume an average subject. Snow and sand need about +1 to +2 stops over what a reflected meter says; dark subjects need less.
- Shutter speeds longer than 30 s need Bulb mode and a remote or timer. Film also needs reciprocity correction at long times.
- Marked shutter speeds are nominal: 1/125 is really 1/128 of a second in the doubling series, so small differences are normal.
- EV says nothing about noise or motion blur. Pick the combination that suits the subject, then let the calculator keep the exposure constant.
Frequently asked questions
What is the formula for exposure value?
EV = log₂(N²/t) with N the f-number and t the shutter time in seconds. To express it at ISO 100, subtract log₂(ISO/100).
What EV is a sunny day?
About EV 15 at ISO 100 for a typical subject in full sun with distinct shadows, EV 16 for snow or sand in sun and EV 14 in hazy sun.
How do I find an equivalent exposure?
Count stops. If you open the aperture one stop, make the shutter one stop faster or the ISO one stop lower. The calculator does the exact maths and rounds to your camera's third-stop settings.
Does ISO change the exposure value?
ISO does not change the light in the scene, but it changes which setting EV exposes it correctly. Each doubling of ISO lets you use a setting one EV higher.
Why does my answer not match a marked shutter speed?
Exact maths rarely lands on a nominal speed. The tool shows the nearest marked value and how many stops it differs by; a third of a stop or less is usually invisible.
Is the sunny 16 rule accurate for digital cameras?
It is a good starting point in clear midday sun at mid latitudes. Morning light, haze and high latitude are dimmer, so check the histogram after the first frame.
Is there an in-depth guide to the Exposure Calculator?
Yes. “Exposure Value Explained: Stops, Sunny 16 and Equivalent Exposures” covers the background, how it works, common pitfalls and worked examples. Read the full guide.
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