Photography / Exposure
Exposure Calculator: Equivalent Aperture, Shutter and ISO
Compare equivalent exposure settings from a reference photograph. Lock any two of aperture, shutter and ISO, solve the third, choose full, half or third stops, and consult an EV100 chart and sunny 16 starting points.
Exposure Calculator: Equivalent Aperture, Shutter and ISO: Keeps shutter time times ISO divided by aperture squared constant. It shows the reference EV at ISO 100, the new settings EV, and the difference caused by stop rounding. The chart lists shutter times for EV100 from -4 to 20 at five apertures. Runs 100% locally in your browser with zero server file uploads.
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Exact solved value: 1/128 s. Rounded result differs by 0 stops in EV100. Positive means less exposure.
EV = log₂(N²/t). EV100 = EV − log₂(ISO/100). Equivalent brightness keeps t × ISO / N² constant. Stop sequences are exact powers of two; printed camera labels may be rounded differently.
Sunny 16 starting points
Use shutter seconds near 1/ISO. These are rough daylight estimates; meter the scene and adjust for the subject.
| Light | Aperture | Shutter at ISO 100 |
|---|---|---|
| Bright snow or sand | f/22 | 1/100 s |
| Direct bright sun | f/16 | 1/100 s |
| Hazy sun | f/11 | 1/100 s |
| Overcast | f/8 | 1/100 s |
| Heavy overcast | f/5.6 | 1/100 s |
| Open shade | f/4 | 1/100 s |
Exposure value chart at ISO 100
Each cell is a shutter time. Move one EV higher to halve the exposure time.
| EV100 | f/1 | f/2 | f/4 | f/8 | f/16 |
|---|---|---|---|---|---|
| -4 | 16 s | 64 s | 256 s | 1024 s | 4096 s |
| -3 | 8 s | 32 s | 128 s | 512 s | 2048 s |
| -2 | 4 s | 16 s | 64 s | 256 s | 1024 s |
| -1 | 2 s | 8 s | 32 s | 128 s | 512 s |
| 0 | 1 s | 4 s | 16 s | 64 s | 256 s |
| 1 | 1/2 s | 2 s | 8 s | 32 s | 128 s |
| 2 | 1/4 s | 1 s | 4 s | 16 s | 64 s |
| 3 | 1/8 s | 1/2 s | 2 s | 8 s | 32 s |
| 4 | 1/16 s | 1/4 s | 1 s | 4 s | 16 s |
| 5 | 1/32 s | 1/8 s | 1/2 s | 2 s | 8 s |
| 6 | 1/64 s | 1/16 s | 1/4 s | 1 s | 4 s |
| 7 | 1/128 s | 1/32 s | 1/8 s | 1/2 s | 2 s |
| 8 | 1/256 s | 1/64 s | 1/16 s | 1/4 s | 1 s |
| 9 | 1/512 s | 1/128 s | 1/32 s | 1/8 s | 1/2 s |
| 10 | 1/1024 s | 1/256 s | 1/64 s | 1/16 s | 1/4 s |
| 11 | 1/2048 s | 1/512 s | 1/128 s | 1/32 s | 1/8 s |
| 12 | 1/4096 s | 1/1024 s | 1/256 s | 1/64 s | 1/16 s |
| 13 | 1/8192 s | 1/2048 s | 1/512 s | 1/128 s | 1/32 s |
| 14 | 1/16384 s | 1/4096 s | 1/1024 s | 1/256 s | 1/64 s |
| 15 | 1/32768 s | 1/8192 s | 1/2048 s | 1/512 s | 1/128 s |
| 16 | 1/65536 s | 1/16384 s | 1/4096 s | 1/1024 s | 1/256 s |
| 17 | 1/131072 s | 1/32768 s | 1/8192 s | 1/2048 s | 1/512 s |
| 18 | 1/262144 s | 1/65536 s | 1/16384 s | 1/4096 s | 1/1024 s |
| 19 | 1/524288 s | 1/131072 s | 1/32768 s | 1/8192 s | 1/2048 s |
| 20 | 1/1048576 s | 1/262144 s | 1/65536 s | 1/16384 s | 1/4096 s |
Changing aperture also changes depth of field. Shutter changes motion blur; ISO changes amplification and image noise. Equivalent settings do not produce identical photographs.
Exposure mathematics
The APEX exposure system relates aperture and time logarithmically: EV = log2(N squared / t). ISO 2720 describes photographic exposure meters; official catalogue: https://www.iso.org/standard/7690.html . The tool compares settings, rather than measuring scene luminance.
Daylight estimates and camera effects
Stanford CS178, Variables that affect exposure: https://graphics.stanford.edu/courses/cs178/applets/exposure.html . Sunny 16 uses f/16 and a shutter time near the reciprocal of ISO in direct bright sunlight; the displayed weather table is a conventional starting guide. Stop calculations retain exact powers of two rather than rounded camera labels.
How to use it
- Enter the reference aperture, shutter time and ISO.
- Choose which setting to solve and enter the other two settings.
- Read the exact and rounded result, review the EV difference and copy the settings.
Privacy & limitations
Camera settings are calculated in your browser and are not uploaded.
Related tools
Frequently asked questions
What is the difference between EV and EV100?
EV = log2(N squared / t) describes aperture and shutter settings. EV100 subtracts log2(ISO / 100), so equivalent brightness can be compared at a common sensitivity.
Why do the numbers differ from camera labels?
The stop grid uses exact powers of two. Camera markings such as f/5.6 and 1/125 are rounded conventions. The exact solved value and the resulting EV difference are shown.
Does equivalent exposure mean the photograph looks the same?
No. Aperture affects depth of field, shutter affects motion blur, and ISO changes amplification and noise. Sunny 16 is a rough daylight starting point, not a substitute for metering.
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