Free photography tool
Exposure Calculator
Start with a correct exposure, then change the aperture, shutter speed or ISO and see what the third setting needs to be to keep the same brightness. Includes EV and Sunny 16.
1. A correct exposure (from your meter or a test shot)
Suits a scene like: bright overcast, no shadows (EV at ISO 100).
2. Change settings, keep the same brightness
Same brightness as f/8, 1/125, ISO 100. Exact value 1/4082, rounded to the nearest third stop.
3. Equivalent exposures at ISO 100
| Aperture | Shutter | Depth of field | Motion |
|---|---|---|---|
| f/1.4 | 1/4000 | Shallow depth, blurry background | Freezes fast action |
| f/2 | 1/2000 | Shallow depth, blurry background | Freezes fast action |
| f/2.8 | 1/1000 | Shallow depth, blurry background | Freezes fast action |
| f/4 | 1/500 | Moderate depth | Freezes people walking |
| f/5.6 | 1/250 | Moderate depth | Freezes people walking |
| f/8 | 1/125 | Deep, most of the scene sharp | Comfortable handheld |
| f/11 | 1/60 | Deep, most of the scene sharp | Comfortable handheld |
| f/16 | 1/30 | Very deep; fine detail can soften slightly | Brace yourself or the camera |
| f/22 | 1/15 | Very deep; fine detail can soften slightly | Brace yourself or the camera |
4. Sunny 16 starting point (no meter needed)
f/16 at 1/100, ISO 100
Shadows: distinct, hard-edged shadows. Shutter is 1 over the ISO.
Light levels by EV (ISO 100)
- EV 16 Bright sun on snow or sand
- EV 15 Bright, direct sun
- EV 14 Hazy sun, soft shadows
- EV 13 Bright overcast, no shadows
- EV 12 Heavy overcast or open shade
- EV 11 Sunset, or deep shade
- EV 9 Neon signs, bright street at night
- EV 7 Lit city streets at night
- EV 5 Typical home interior at night
- EV 3 Floodlit buildings, candlelight
- EV -2 Moonlit landscape
How to use the exposure calculator
- Enter a correct exposure.Take it from your camera's meter, a test shot that looked right, or the Sunny 16 panel if you have no meter.
- Choose what to work out: shutter speed, aperture or ISO.
- Set the other two to what you want. For example, f/2.8 for a blurry background at ISO 400.
- Read the answer. It is rounded to the nearest third stop your camera offers, with the exact value shown beside it.
The equivalent exposures table lists every full-stop aperture at the current ISO, with a note on how deep the focus is and whether the shutter speed freezes motion.
How aperture, shutter speed and ISO trade off
Exposure is the total light the sensor records. Aperture controls how wide the lens opens, shutter speed controls for how long, and ISO controls how strongly the camera amplifies what arrives. Change one by a stop and you can balance it with a stop in the opposite direction on another, and the photo stays the same brightness. The exposure triangle guide explains each setting in depth.
What changes is the look. Aperture sets depth of field, which the depth of field calculator measures in metres. Shutter speed decides whether movement freezes or blurs. ISO adds noise as it rises.
Worked example: from f/8 to a blurry background
On a bright overcast day the meter reads f/8 at 1/125, ISO 100. That is EV 13, typical for bright cloud with no shadows.
To blur the background, open the aperture. Each stop wider halves the time the shutter needs to stay open:
| Aperture | Shutter at ISO 100 | What changes |
|---|---|---|
| f/2.8 | 1/1000 | Shallow focus, freezes fast action |
| f/4 | 1/500 | Shallow focus, freezes people walking |
| f/5.6 | 1/250 | Moderate depth |
| f/8 | 1/125 | The meter reading |
| f/11 | 1/60 | Deep focus, still fine handheld |
| f/16 | 1/30 | Very deep focus, brace the camera |
Indoors at night the meter might read f/4 at 1/60, ISO 800 (about EV 7 at ISO 100). Open to f/2 and the same brightness comes at 1/250, fast enough to freeze someone talking. Keep 1/125 at f/2.8 instead and you need about ISO 800.
The Sunny 16 rule
Sunny 16 is a way to expose correctly without a light meter. In bright sun with crisp shadows, use f/16 and a shutter speed of 1 over your ISO. Then open the aperture as the light drops:
| Conditions | Aperture | Shadows look |
|---|---|---|
| Snow or sand in sun | f/22 | Very dark and crisp |
| Bright sun | f/16 | Distinct, hard edges |
| Slight overcast | f/11 | Soft edges |
| Overcast | f/8 | Faint |
| Heavy overcast | f/5.6 | None |
| Open shade or sunset | f/4 | No direct sun |
At ISO 100 in full sun that gives f/16 at 1/100, which is about EV 14.6. Any equivalent works too: f/8 at 1/400 or f/5.6 at 1/800 let in the same light. Melbourne's softer evening light is covered in the golden hour photography guide, and darker scenes in the night photography settings guide.
How it is calculated
The calculator uses the standard exposure value formula:
EV = log₂(N² / t), where N is the f-number and t is the shutter time in seconds- EV at ISO 100:
EV₁₀₀ = log₂(N² / t) − log₂(ISO / 100)
Two settings give the same brightness when their EV at ISO 100 matches, so the calculator rearranges the formula to solve for the missing setting. f/8 at 1/125 is log₂(64 × 125), which is 13.0. Results are rounded to the nearest third stop, the steps most cameras use. Scene descriptions for each EV are typical values, since real light varies.
Everything runs in your browser. Nothing is uploaded and there is no sign-up.
Common mistakes
- Mixing up which way the aperture numbers go. f/2.8 is wider and brighter than f/8. Bigger number, smaller hole.
- Forgetting the side effects. An equivalent exposure is the same brightness with a different look: a slow shutter can blur people, a high ISO adds noise.
- Trusting Sunny 16 on a backlit subject. The rule assumes the sun lights the subject. A face in shadow needs more light.
- Starting from a bad reading. If the first exposure was too dark, every equivalent will be too dark by the same amount.
Frequently asked questions
What is EV in photography?
EV, or exposure value, is a single number for a combination of aperture and shutter speed. Each step of 1 EV is one stop: double or half the light. Quoted at ISO 100, EV also describes how bright a scene is, from about EV 15 in bright sun to around EV 5 in a home at night.
What is the Sunny 16 rule?
On a sunny day with distinct shadows, set the aperture to f/16 and the shutter speed to 1 over the ISO. At ISO 100 that is f/16 at 1/100 (or 1/125, the nearest full stop). Open up one stop for each step of cloud: f/11 for slight overcast, f/8 for overcast, f/5.6 for heavy overcast, f/4 for open shade.
What is an equivalent exposure?
Different settings that let in the same total amount of light. f/8 at 1/125, f/4 at 1/500 and f/16 at 1/30 all produce the same brightness at the same ISO. They look different: the f/4 version has a shallower depth of field and freezes more motion.
What is a stop of light?
A stop is a doubling or halving of light. Going from 1/125 to 1/250, from f/8 to f/11, or from ISO 400 to ISO 200 each removes one stop. Most cameras also offer third stops, which is why you will see values like 1/160, f/7.1 and ISO 320.
Why does the calculator round my result?
Cameras only offer set values, usually in third stops. The calculator works out the exact answer, shows it, and rounds to the nearest setting a camera actually has, so the difference is never more than a sixth of a stop.
Does this exposure calculator work for film?
Yes. The maths of aperture, shutter speed and ISO is the same for film. Use the film's box speed as the ISO. For exposures longer than about one second, many films need extra time because of reciprocity failure, which this calculator does not include.
Is EV the same as exposure compensation?
They use the same unit. Exposure compensation moves the camera's metered exposure up or down by a number of stops, written as EV, for example +1 EV to brighten a snowy scene. The EV in this calculator describes a specific combination of settings.
Learn it with a camera in your hands
Balancing aperture, shutter speed and ISO by hand is the core of the beginner course. You set all three yourself on your own camera and see the result as the light changes across the city.
The beginner photography course in Melbourne is three hours on foot through the CBD, on your own camera, in full manual, with two students at most. $499.