Exposure Triangle Calculator

Frequently Asked Questions

What is EV?

Exposure Value is a single number representing total exposure brightness. Two settings combinations with the same EV produce the same image brightness, even though the aperture, shutter speed, and ISO may differ.

How do I freeze motion?

Use 1/1000 s or faster for sports and fast wildlife; 1/500 s for most running subjects; 1/125-1/250 s for general handheld shooting.

What reference settings work for common situations?

Sunny day: f/11, 1/200 s, ISO 100. Overcast outdoor: f/8, 1/125 s, ISO 100. Indoor ambient: f/2.8, 1/30 s, ISO 3200.

When do I need a tripod?

Generally for shutter speeds slower than about 1/15 s, and always for deliberate long exposures (seconds, minutes) where even subtle camera movement would blur the image.

Does ISO really affect exposure or just brightness?

ISO amplifies the signal from the sensor, so a higher ISO produces a brighter image from the same light. The trade-off is increased digital noise and reduced dynamic range at high values.

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Estimates for informational purposes only.

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How It Works

Exposure is determined by three interdependent settings: aperture, shutter speed, and ISO. Change one and you must adjust another to keep the same brightness. The overall brightness level is described by the Exposure Value (EV): EV = log2(f^2 / (shutter_time x ISO / 100)) + 1, where f is the f-number and shutter_time is in seconds.

To hold a constant EV while changing one setting, the calculator solves for the locked variable. For example, if you lock shutter speed and open the aperture by two stops, the ISO must drop by two stops to preserve the same brightness. Enter your starting values, choose which parameter to keep constant, and the tool shows you the balanced combination plus an EV description of the scene brightness.

Aperture controls depth of field: a wider aperture (lower f-number) blurs backgrounds more. Shutter speed controls motion: a faster shutter freezes action while a slow shutter introduces blur. ISO controls sensor sensitivity and digital noise: higher ISO brightens the image but adds grain.

Use Cases

The exposure triangle governs every creative and technical exposure decision:

Sports and wildlife: lock a fast shutter (1/1000 s or faster) to freeze motion, then adjust aperture and ISO to match the light

Portraits: lock a wide aperture for shallow depth of field and solve for shutter and ISO

Long exposures: lock a slow shutter to blur water or light trails, then stop down to compensate

Low-light shooting: understand the trade-off between raising ISO and slowing the shutter or opening the aperture

Teaching: visualize how the three levers interact without trial-and-error on the camera

Tips

A higher f-number means a smaller aperture opening and less light - the opposite of what beginners expect.

Enter shutter speed as a fraction (1/200) rather than a decimal (0.005) to avoid confusing the input format.

Use EV reference values as a sanity check: a sunny day is about EV 15, overcast outdoor EV 12-13, indoor ambient EV 7-9.

The slowest safe handheld shutter speed is roughly 1/(focal length x crop factor) seconds - for a 50 mm lens on full-frame that is about 1/50 s.

When raising ISO above 1600-3200, check if you can open the aperture or slow the shutter instead to keep noise lower.

FAQ