Exposure Value (EV) Calculator — Aperture, Shutter, ISO

Real-world use cases

• Meter a scene without a light meter

  You are on a bright street at noon with no meter handy. The Sunny-16 reference puts direct sun near EV 15. Type f/16 and 1/125 s at ISO 100 and confirm the tool reads about EV 15, then trust any equivalent pair the dial offers — f/8 at 1/500 s or f/11 at 1/250 s — to keep the same exposure while you pick the depth of field you actually want.

• Trade aperture for shutter to control motion or depth

  A portrait at f/8 and 1/250 s freezes the subject but the background is too busy. You want f/2.8 for separation. Lock the EV, switch the solver to shutter, set f/2.8, and read the faster shutter — about 1/2000 s — that holds identical exposure. Now you have the same brightness with a soft background, decided before you raise the camera.

• Plan an ISO bump in fading light

  Light is dropping at the end of a shoot and your shutter is already at the hand-holdable limit. Enter your current aperture, shutter and ISO 100, note the EV, then bump ISO to 800 and watch the metered EV fall three stops — exactly the brightness you would lose. That tells you how much you must open up or slow down to compensate before grain becomes the only lever left.

• Teach the exposure triangle with concrete numbers

  Explaining stops to a beginner lands better with figures than words. Show that f/4 at 1/500 s and f/8 at 1/125 s both compute to the same EV, then change ISO and watch the EV move by whole stops. The shareable URL lets you hand a student a link that opens the exact example, so the lesson reproduces without a screenshot.

• Double-check a manual exposure before a long take

  Before a long exposure of a night cityscape you want to be sure the settings are sane. Punch in f/11, 8 s and ISO 200 and read the EV; compare it against the night-scene rows in the reference table. If the number is far from the expected range you have caught a dial error before burning a multi-second frame.

Common pitfalls

• Forgetting that EV is defined at ISO 100. The bare formula EV = log2(N²/t) assumes ISO 100; if you shoot at ISO 400 the scene EV is two stops lower than the aperture-shutter pair alone suggests. Enter the real ISO so the tool subtracts log2(ISO/100) instead of reading the ISO-100 number as if it were the scene brightness.

• Mixing up the shutter format. A shutter of 250 means 250 seconds, not 1/250 s. Type fast speeds as the fraction 1/250, and reserve plain numbers for whole-second exposures. Entering 250 where you meant 1/250 throws the EV off by about 16 stops and the result looks absurd.

• Treating a smaller f-number as less light. f/2.8 is a wider aperture than f/8 and lets in more light, so it is the larger opening despite the smaller printed number. Because the formula uses N², halving the f-number raises the light by two stops, which is easy to invert if you read the number as a plain size.

Privacy