Exposure Calculator

What is an exposure calculator?

An exposure calculator turns the three camera settings that control brightness—aperture, shutter speed and ISO—into a single number called exposure value (EV). That number lets you compare scenes, match settings across cameras, and trade one setting for another without changing overall exposure. This tool uses the standard photographic EV equation referenced to ISO 100, so the results line up with light meters, charts and textbooks.

Photographers reach for an exposure calculator when they need to freeze motion without underexposing, keep depth of field deep without a shaky shutter, or stay at base ISO for maximum dynamic range. Instead of guessing, you enter the two settings you must keep and read the third—or simply inspect the EV of a combination you already plan to shoot.

How the exposure triangle works

Aperture (f-number) controls how wide the lens diaphragm opens. Each full stop (for example f/2.8 to f/4) halves or doubles the light. Shutter speed controls how long the sensor is exposed; doubling the time adds one stop. ISO controls the amplification of the sensor signal; doubling ISO also adds one stop of brightness but typically adds noise. Together these three axes form the exposure triangle: change one side and you can compensate on another to hold the same EV.

Mathematically the relationship is:

where N is the f-number, t is shutter time in seconds, and ISO is the sensitivity setting. At ISO 100 the second term is zero, which is why EV charts are often quoted “at ISO 100.” Raising ISO by one stop lowers the EV number by one for the same aperture and shutter—meaning the scene would need less light to look the same.

Typical EV ranges

Bright sun on a clear day sits around EV 14–16 at ISO 100. Open shade or heavily overcast skies fall near EV 12–13. A well-lit indoor room might be EV 5–8. Night city streets with street lamps often land around EV 3–6, while a dim restaurant or stage can drop below EV 2. Knowing these ballparks helps you decide whether a combination is realistic before you lift the camera.

Worked example

Suppose you want f/4, 1/100 s (0.01 s) and ISO 100. Plugging into the formula gives EV ≈ 12. That is consistent with daylight under clouds or open shade. If you open to f/2.8 (one stop more light) and keep the same shutter and ISO, EV becomes ≈ 11—the image would be one stop brighter unless you shorten the shutter or lower ISO.

Tips for practical use

• Lock shutter for motion (sports, wildlife), then solve aperture or ISO with companion tools on this site.
• Lock aperture for depth of field (portraits vs landscapes), then adjust shutter and ISO.
• Prefer base ISO when light allows; raise ISO only after aperture and shutter are constrained.
• Remember that in-camera meters use calibration constants and scene interpretation—EV from the formula is the pure photometric relationship.

FAQ

Why does my camera meter show a different value?

Meters aim to place the scene at middle gray and may bias for highlights or matrix patterns. The calculator reports the mathematical EV of your three settings, not a recommendation for a specific scene.

Does sensor size affect EV?

No. Exposure value depends only on N, t and ISO. Sensor size affects depth of field, field of view and noise characteristics, not the EV equation.

What is the difference between EV and LV?

Light value (LV) often refers to scene luminance at ISO 100. EV is used both for settings and for scene brightness depending on context; this calculator uses the settings-based definition above.

Building a personal exposure habit

Start by noting the EV of light you shoot in most often—office windows, open shade, noon sun, stage spots. After a few sessions you will recognize that “this room is about EV 7 at ISO 100” and can pre-set aperture and shutter before metering. The calculator accelerates that learning: punch in the settings you used on a successful frame and store the EV mentally as a reference for similar spaces.

When mixing continuous light and flash, compute the ambient EV first, then decide how many stops below ambient the flash should sit for fill, or how many stops above for dominant key light. Equivalent exposures matter when you change shutter to control ambient while holding aperture for depth of field: raise ISO or open the lens to keep the same EV if ambient must stay constant. Conversely, leave EV alone when you intentionally want ambient to darken behind a frozen subject.

Log keepers and cinematographers often document setups as EV plus white-balance notes. That makes recreating a look on another stage faster than copying three independent numbers that may not be available on every body. Pair this tool with the aperture, shutter and ISO solvers when one axis is locked by creative constraints.

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