Exposure Calculator

How to use it

1. Set the three exposure values you know — aperture (f-number), shutter time and ISO — plus any exposure compensation in 1/3-stop steps.
2. Pick what to solve for: shutter time, aperture or ISO.
3. The equivalent setting appears immediately, exact value first, nearest standard stop in brackets.
4. Read the comparison table for equivalent shutter times across common ISO values at your aperture.

Common use cases

• ISO changes on the fly — raise ISO in dark light and find the shutter that keeps the same exposure.
• Freezing motion — shorten the shutter and solve for the aperture that holds exposure.
• Balancing flash and ambient — compare combinations before a shoot instead of guessing in the field.
• Learning exposure — hold brightness fixed and watch how the three values trade off.

Why it stays private

Every conversion is arithmetic on the numbers you typed. Nothing is sent anywhere, and the calculator works offline.

FAQ

Q: What math does it use? A: The standard exposure-value relation, EV = log2(f-number squared over shutter time), adjusted for ISO and compensation. Results are exact for that model.

Q: Are results rounded? A: The main result is exact; the comparison table rounds each shutter to the nearest standard stop so it matches real camera dials.

Q: Does it model lens transmission or metering mode? A: No. It is pure EV math — real meters and lenses vary, so treat results as a starting point, not ground truth.