π‘ Equivalent Exposure Calculator
Lock the exposure value, explore every equivalent aperture, shutter, and ISO combo.
Locked exposure value for your settings
How to Use This Calculator
Exposure is a three-way trade: aperture controls depth of field, shutter controls motion, ISO controls noise, and all three combine into one brightness. Enter the exposure you have (or the one your meter suggests) and this calculator locks its exposure value, then lists every equivalent combination across full stops so you can pick the look you want without changing the brightness.
Select your starting Aperture, Shutter Speed, and ISO. Use whatever your camera metered, or the exposure you are currently shooting.
Read the locked EV at the top. Every row in the table below matches this exact brightness: same total light, different creative trade-offs.
Scan the equivalent pairs. Want shallower depth of field? Move up the aperture column and take the faster shutter it pairs with. Need to freeze motion? Pick your shutter first and read the matching aperture.
Check the ISO ladder. Each ISO step shows the same EV shifted: higher ISO buys you faster shutters or smaller apertures at the cost of noise. Pick the lowest ISO that still gives you a workable pair.
The Formula: Exposure Value
Exposure value compresses the aperture-shutter relationship into a single number. Because f-numbers are ratios of focal length to aperture diameter, the light they pass scales with N squared, and the shutter contributes its time directly; the base-2 logarithm turns those multiplications into simple addition. An EV of 12 at ISO 100 is the classic sunny-day-with-clouds brightness; EV 15 is harsh midday sun.
Equivalent exposures are just EV arithmetic. Opening the aperture one stop (say f/8 to f/5.6) doubles the light, so the shutter must halve its time (1/125 to 1/250) to hold EV constant. ISO shifts the whole scale: at ISO 400 the sensor is four times as sensitive as ISO 100, so the required EV drops by 2. The calculator applies this to full-stop ladders of apertures (1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22), shutters, and ISOs, and pairs them so every combination in a row shares your locked EV.
Worked Example
Starting point: f/2.8, 1/125 s, ISO 400. Settings EV = log2(2.8^2 / 0.008) = log2(7.84 / 0.008) = log2(980) = 9.94. At ISO 400 the sensor is four times as sensitive as ISO 100, so the scene brightness is 9.94 + 2 = EV 11.94 at ISO 100 reference. The calculator locks EV 11.9 and lists pairs like f/4 at 1/60, f/5.6 at 1/30, f/8 at 1/15, f/2 at 1/250, f/1.4 at 1/500, all at ISO 400.
Now the creative move: you want f/1.4 bokeh in this light. The table shows f/1.4 pairs with 1/500 at ISO 400. Your subject is a toddler who never sits still, so 1/500 is perfect, but ISO 400 looks cleanest on your camera and you would rather be at ISO 100. The ISO ladder shows the ISO 100 row: f/1.4 would need 1/125, too slow for the toddler. Compromise: ISO 200, f/1.4, 1/250. Same brightness, workable motion freeze, minimal noise.
Practical Tips
Learn the sunny 16 anchor: bright sun is f/16 at 1/ISO, so ISO 100 gives f/16 at 1/100. From there you can walk the equivalents mentally: f/11 at 1/200, f/8 at 1/400, f/5.6 at 1/800. This calculator is the training wheels for that mental math; after a month of checking your guesses against it, you will stop needing it.
Use equivalents to escape bad light decisions. The classic beginner trap is shooting f/22 for "maximum sharpness" in dim light and getting a blurry 1/4 s handheld shot. The table shows f/8 at 1/30 is the same brightness and far sharper in practice. When in doubt, the table row with the fastest comfortable shutter usually wins for handheld work.
Frequently Asked Questions
What are equivalent exposures?
Exposures that let in the same total amount of light: f/8 at 1/125 is equivalent to f/5.6 at 1/250 and f/11 at 1/60. Each pair trades one stop of aperture for one stop of shutter speed. The exposure value (EV) is identical, so the brightness matches, but depth of field and motion blur differ.
How is exposure value (EV) calculated?
For ISO 100, EV = log2(N^2 / t), where N is the f-number and t is the shutter time in seconds. Each increase of 1 EV means half the light. Doubling the ISO lowers the required EV by 1: a scene at EV 12 needs ISO 100 at f/8 and 1/125, or ISO 200 at f/8 and 1/250.
Why would I want a different equivalent exposure?
Creative control. You might want f/2.8 for creamy bokeh but the light demands f/8 at 1/125; the equivalents tell you f/2.8 needs 1/1000 to match. Or you need 1/500 to freeze a runner and want to know which aperture pairs with it. Equivalents separate brightness from the look.
Do third-stop clicks break the full-stop table?
No. The full-stop table gives you the anchor points; your camera's third-stop clicks sit between them. If the table says f/5.6 at 1/250 and you need a touch more depth of field, two clicks narrower on the aperture (toward f/6.3, f/7.1) with two clicks slower on the shutter keeps the exposure equivalent.
What if my camera cannot reach a listed shutter speed?
That is exactly what the table reveals: if the equivalent shutter is 1/8000 and your camera tops out at 1/4000, that combination is impossible in this light without an ND filter. Pick the next row down, or add the ND filter strength to shift every row. The ISO column offers another escape hatch.
How does ISO fit into equivalent exposures?
ISO is the third side of the triangle. Raising ISO one stop lets you use one stop less light from aperture and shutter combined. The calculator shows an ISO ladder: for each ISO step, it lists the matching aperture and shutter pairs, so you can see the cost of going to ISO 6400 in depth of field and motion terms.