Exposure Equivalents Calculator
Find equivalent camera settings that produce the same exposure value when you change aperture, shutter speed, or ISO. Useful any time you want to swap depth-of-field or motion blur without altering overall image brightness.
Last updated: May 2026
Equivalent Shutter Speed
0.4 s
At 0.1 s and longer, motion blur is unavoidable handheld. Use a tripod and remote release; subjects moving during a 0.4 s exposure will streak.
The equivalent shutter speed comes from the reciprocity formula; these bands reflect the photographic rule that handholding usually requires faster than about 1/60 s (0.0167 s).
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About this calculator
Photographic exposure is the product of three variables — aperture, shutter speed, and ISO — measured in "stops". Every one-stop change in any variable is either a doubling or a halving of light. Equivalent exposure is the same total light captured but with a different mix of the three: f/8 at 1/125 at ISO 100 captures the same amount of light as f/5.6 at 1/250 at ISO 100, and the same as f/8 at 1/60 at ISO 50. This calculator gives you the full reciprocal table for any starting exposure.
The exposure triangle in stops
Aperture: doubling area = one stop. f/2.8 → f/4 → f/5.6 → f/8 → f/11 → f/16 → f/22 each halves the light. Shutter speed: doubling time = one stop. 1/1000 → 1/500 → 1/250 → 1/125 → 1/60 → 1/30 each doubles the light. ISO: doubling sensitivity = one stop. 100 → 200 → 400 → 800 each doubles the light. To hold exposure constant, any change in one has to be matched by an equal-and-opposite change in one of the other two.
When each variable matters
Aperture controls depth of field — wider (smaller f-number) = less DoF, more blur behind and in front of the subject. Shutter speed controls motion — faster = frozen action, slower = motion blur or streaks. ISO controls sensor noise — lower = cleaner shadows, higher = noisier but usable in low light. The equivalent-exposure table lets you decide which of those trade-offs matter most for a given shot and adjust the other two to compensate.
Reciprocity failure
Above about 1 second on film (some films sooner), the linear relationship between shutter time and exposure breaks down — the film needs disproportionately longer to gain another stop of exposure. Modern digital sensors don't have this problem in the same way, but very long exposures (30+ seconds) still show non-linear noise buildup. The reciprocity-failure column of the table adjusts recommended long exposures if the film-mode toggle is on.
Exposure compensation vs equivalent exposure
These are different things. Exposure compensation (EV +/-) intentionally over- or under-exposes to correct for a metering that's fooled by the scene (snow, backlit subject). Equivalent exposure is holding total exposure constant while changing the mix. The calculator here is for the second case.
How to use
Suppose your current settings are f/2.8, 1/200 s shutter, ISO 400, and you want to switch to f/8 to gain more depth of field while keeping the same exposure. Step 1: Square both apertures: 2.8² = 7.84, 8² = 64. Step 2: Apply the formula: targetShutter = (7.84 × (1/200) × 400) / 64 = (7.84 × 0.005 × 400) / 64 = 15.68 / 64 ≈ 0.245 s. Step 3: Set your camera to approximately 1/4 s at f/8, ISO 400. The scene will be exposed identically to the original f/2.8 shot.
Frequently asked questions
How do I calculate equivalent exposure when changing both aperture and ISO at the same time?
When changing multiple exposure parameters simultaneously, you need to account for each change's effect on light. Start from the fundamental exposure equation: EV is constant when (ISO × shutterSpeed) / aperture² stays equal. Rearrange to solve for the one unknown you want to find. For example, to find the new shutter speed when both aperture and ISO change: newShutter = (oldAperture² × oldShutter × oldISO) / (newAperture² × newISO). This calculator assumes ISO is held constant, so if you change ISO, apply the ratio manually as an additional multiplier.
What is a stop in photography and how does it relate to equivalent exposure?
A stop is a doubling or halving of light. Opening the aperture by one stop (e.g., f/4 to f/2.8) doubles the light; closing it halves the light. Similarly, doubling the shutter speed or doubling the ISO each adds one stop of exposure. Equivalent exposures are combinations that differ by equal and opposite stops across parameters, so the total light remains the same. The formula captures this mathematically through the squared aperture ratio, reflecting that aperture area scales with the square of the f-number.
When would a photographer need to calculate equivalent exposure settings in the field?
A common scenario is switching lenses with different maximum apertures — for example, moving from a fast f/1.8 prime to an f/5.6 zoom. You need to know how much to adjust shutter speed or ISO to preserve the correct exposure. Another situation is intentional creative change: you want a longer shutter to blur water, which requires closing down the aperture to compensate. Sports photographers use equivalent exposure when the minimum shutter speed for freezing action forces them to recalculate ISO. Understanding equivalent exposures prevents over- or under-exposed shots during quick setting changes.
What is an equivalent exposure?
The same total amount of light captured, but with a different combination of aperture, shutter speed, and ISO. f/8 at 1/125 at ISO 100 is equivalent to f/5.6 at 1/250 at ISO 100 (one stop less light from aperture, one stop more from shutter speed) — same exposure, different depth of field and motion look.