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Exposure Triangle Calculator

PhotographyExposure and Camera Settings
Metered exposure

In seconds: 1/125 s is 0.008, 1/60 s is 0.0167.

What you change
Solve for
Equivalent setting —
Setting solved
—
New combination
—
Scene EV at ISO 100
—
EV of new aperture and shutter
—
Change per setting
—

The exposure triangle links aperture, shutter time and ISO: light recorded scales with time × ISO ÷ f-number². Keep that product fixed and the brightness stays the same. Example: f/16 at 1/125 s and ISO 100 in sun equals f/8 at 1/500 s, because opening two stops lets in four times the light and the shutter must cut it by four.

About this tool

Photographers trade one setting for another all the time: a wider aperture to blur a background, a faster shutter to freeze a runner, a higher ISO when the light fades. Each change has to be paid back by the other two settings or the frame gets darker or brighter. Enter the exposure your meter gave you, pick which setting to solve for, and set the other two to the values you want. The calculator returns the matching third setting, the scene's exposure value at ISO 100, and how many stops each setting moved. It works with exact values, so the answer may land between the marked stops on your dial; pick the nearest one and expect up to a third of a stop of difference. It does not model reciprocity failure on film for exposures longer than about one second.

How to use it

  1. Enter the metered exposure

    Type the f-number, shutter time (s) and ISO that gave a correct exposure.

  2. Choose what to solve for

    Pick shutter time, aperture or ISO; the other two become fields you set.

  3. Set the two settings you want

    Enter the new aperture, shutter time or ISO, whichever fields are showing.

  4. Read the equivalent setting

    The result shows the third setting, the full new combination and the stop change for each part.

Examples

Sunny 16 opened to f/8

Aperture (f-number)
16
Shutter time
0.008
ISO
100
Solve for
Shutter time
New aperture
8
New ISO
100

Result Equivalent setting: 1/500 s
Setting solved: Shutter
New combination: f/8, 1/500 s, ISO 100
Scene EV at ISO 100: 15.0
EV of new aperture and shutter: 15.0
Change per setting: shutter -2, aperture -2, ISO 0 stops

  1. Exposure stays equal when t × ISO ÷ N² is unchanged: 0.008 × 100 ÷ 16² = 0.003125
  2. t₂ = 0.008 × (8² ÷ 16²) × (100 ÷ 100) = 0.002 s ≈ 1/500 s
  3. EV100 of the scene = log₂(16² ÷ 0.008) − log₂(100 ÷ 100) = 14.97

Bright sun meters f/16, 1/125 s at ISO 100. Opening two stops for shallower depth of field needs a shutter four times faster.

Freeze motion at 1/250 s

Aperture (f-number)
2.8
Shutter time
0.016667
ISO
800
Solve for
ISO
New aperture
2.8
New shutter time
0.004

Result Equivalent setting: ISO 3333
Setting solved: ISO
New combination: f/2.8, 1/250 s, ISO 3333
Scene EV at ISO 100: 5.9
EV of new aperture and shutter: 10.9
Change per setting: shutter -2.06, aperture 0, ISO 2.06 stops

  1. Exposure stays equal when t × ISO ÷ N² is unchanged: 0.016667 × 800 ÷ 2.8² = 1.700714
  2. ISO₂ = 800 × (0.016667 ÷ 0.004) × (2.8² ÷ 2.8²) = 3333.4
  3. EV100 of the scene = log₂(2.8² ÷ 0.016667) − log₂(800 ÷ 100) = 5.88

A room meters f/2.8, 1/60 s, ISO 800. Moving to 1/250 s at the same aperture costs about two stops, which the ISO has to make up.

How it is calculated

t₁ × ISO₁ ÷ N₁² = t₂ × ISO₂ ÷ N₂²; EV100 = log₂(N² ÷ t) − log₂(ISO ÷ 100)

N
f-number (aperture)
t
shutter time, s
ISO
sensor or film sensitivity
EV100
exposure value referred to ISO 100

Light reaching the sensor is proportional to the shutter time and to the area of the aperture, which falls with the square of the f-number. ISO scales how much signal a given amount of light produces. Holding t × ISO ÷ N² constant keeps the image brightness the same, so any one setting can be solved from the other two. One stop is a factor of two: doubling time or ISO, or multiplying the f-number by √2 (about 1.4). The exposure value uses the same relation on a base-2 log scale.

When not to use it

  • Film exposures longer than about one second need a reciprocity correction this formula leaves out.
  • Flash exposure depends on flash power and distance, not shutter time, once the shutter is at or below sync speed.

Common mistakes

  • Typing 125 for 1/125 s; the shutter field takes seconds, so enter 0.008.
  • Treating f/4 to f/8 as one stop; it is two stops, a quarter of the light.
  • Forgetting that a variable-aperture zoom changes its widest f-number as you zoom.

Frequently asked questions

Why does a smaller f-number mean more light?

The f-number is focal length divided by the aperture diameter. f/4 has an opening twice as wide as f/8, and the area grows with the square of the diameter, so f/4 passes four times the light of f/8, which is two stops.

How do I enter a shutter speed like 1/250?

Divide 1 by the denominator: 1/250 s is 0.004 seconds, 1/60 s is about 0.0167 and 1/1000 s is 0.001. Long exposures go in directly, so a 2-second exposure is 2. The result is shown back in the familiar 1/x form.

What does EV at ISO 100 tell me?

It describes how bright the scene is, independent of the settings you chose. Bright sun is about EV 15, an overcast day about EV 12, a lit room around EV 7 and a street at night around EV 3 to 5. Every combination with the same EV at the same ISO gives the same exposure.

Why is my answer not a standard shutter speed or f-stop?

The calculation is exact, while cameras step in thirds or halves of a stop. 1/450 s, for instance, sits between 1/400 and 1/500. Choosing the nearest marked value changes the exposure by a third of a stop at most, which is usually within the latitude of a raw file.

Does raising ISO add light?

No. ISO amplifies the signal from the light that already reached the sensor, so it brightens the image without collecting more photons. That is why high ISO brings visible noise: the noise in a dim capture is amplified along with the picture.

Which setting should I change first?

Decide what the picture needs. Aperture controls depth of field, shutter time controls motion blur and camera shake, and ISO controls noise. Fix the one that matters most for the subject, then let the calculator find the setting you care about least.

Cite this tool

Using this tool in an assignment, article or report? Copy a citation, or a link for your website.

APA

Tools Directory Editorial Team. (2026, October 16). Exposure Triangle Calculator. Tools Directory. Retrieved October 27, 2026, from https://tools.milunir.com/photography/exposure-and-camera-settings/exposure-triangle-calculator/

MLA

Tools Directory Editorial Team. “Exposure Triangle Calculator.” Tools Directory, 16 Oct. 2026, https://tools.milunir.com/photography/exposure-and-camera-settings/exposure-triangle-calculator/. Accessed 27 Oct. 2026.

Chicago

Tools Directory Editorial Team. “Exposure Triangle Calculator.” Tools Directory. Last modified October 16, 2026. Accessed October 27, 2026. https://tools.milunir.com/photography/exposure-and-camera-settings/exposure-triangle-calculator/.

Link<a href="https://tools.milunir.com/photography/exposure-and-camera-settings/exposure-triangle-calculator/">Exposure Triangle Calculator – Tools Directory</a>