Use the free Sunny 16 Calculator below. Everything runs in your browser, with no sign-up and no upload.
Your camera battery died, or you are shooting an old film camera with no meter at all. You can still get the exposure right in daylight. Photographers have used the Sunny 16 rule for generations, and it works because sunlight is remarkably consistent.
What is Sunny 16 Calculator?
The Sunny 16 rule says: on a bright sunny day, set the aperture to f/16 and the shutter speed to the reciprocal of the ISO. At ISO 100 that is 1/100 second; at ISO 200 it is 1/200 second. For other weather you open up: slight overcast costs one stop, overcast two stops, heavy overcast or open shade three stops, and sunset about four stops. The calculator applies those adjustments and converts the result to any aperture you prefer.
How it works
Sunlight at midday is a known quantity, which is why the rule holds up so well. The calculator starts from the Sunny 16 baseline for your ISO, multiplies the shutter time by two for each stop of dimmer weather, and then adjusts for your chosen aperture. A wider aperture needs a faster shutter; a narrower aperture needs a slower one. The maths is the same stop arithmetic used by every light meter, only done here by hand, in the open.
How to use it
- Judge the light honestly: bright sun with hard shadows is Sunny 16; soft shadows mean overcast.
- Enter your film or sensor ISO.
- Pick the aperture you want to shoot at.
- Set the shutter speed the calculator gives you, and take a test shot if your camera shows a histogram.
Worked example
You are shooting ISO 200 film on a bright day and you want f/8 for a portrait. The rule starts at f/16 and 1/200 second. Opening to f/8 is two stops more light, so the shutter must go two stops faster: 1/800 second. If clouds roll in and the light becomes plain overcast, add two stops back, and you land near 1/200 second at f/8. One rule, two very different days, both handled.
Tips and limits
Sunny 16 is a starting point, not a promise. It is least reliable near sunrise and sunset, in snow or on a beach where reflected light fools the eye, and under trees where the light is patchy. In those cases, meter if you can, or bracket: take one shot at the calculated setting, one a stop brighter and one a stop darker, and keep the best. With digital cameras, check the histogram after the first frame; with film, a little overexposure is usually safer than underexposure for negative film.
Please note: photography exposure tools are educational calculators. Sunny 16 and Zone System figures are starting-point rules of thumb, and a meter reading governs in real shooting. Time-lapse figures assume the camera can sustain the interval, and buffer or card limits may intervene.
Frequently asked questions
Does Sunny 16 work at night or indoors?
No. It is a daylight rule only. Night light varies enormously from street to street, so a meter or trial shots are the only honest approach.
What if my camera cannot set the exact shutter speed?
Use the nearest speed. Sunny 16 settings are approximate by nature, and a third of a stop either way is well inside the rule’s margin.
Is Sunny 16 still useful with a modern camera?
Yes, as a sanity check. If your meter suggests something wildly different from Sunny 16 in bright sun, something is wrong: a wrong ISO, exposure compensation left on, or a lens problem.
Try the calculator above with your own numbers, and use the result as a planned starting point for your next shoot. A few minutes of planning before you press the shutter usually saves a whole session of corrections afterwards.
Pingback: Equivalent Exposure Calculator - Keep the Same Light When You Change Aperture or Speed