Photography Calculators

Exposure & light

Sunny 16 Calculator

Sunny 16: in hard sun, f/16 and a shutter of 1/ISO. Slight overcast is a stop less light, overcast two, heavy overcast three, open shade about four. Bright sand or snow is a stop more — faster shutter, not a wider aperture, so you do not blow the whites. It is a starting point. If the sky is not a textbook sky, meter or chimp a test shot.

Inputs

Units

Film box speed or the ISO you intend to set.

Stops relative to hard sun. Positive is brighter (sand/snow).

Results

Aperture
16f/

Always f/16 in this rule; change shutter for conditions.

Shutter
0.010000s

Shutter time in seconds; 1/125 is 0.008.

Shutter reciprocal
100

125 means 1/125 s.

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Calculation method

The rule fixes aperture at f/16. In sun, shutter time is 1/ISO seconds (ISO 100 → 1/100 s). Condition stops scale that time: brighter sand or snow divides time by two (faster shutter); overcast multiplies time (slower shutter) by two, four or eight for −1, −2, −3. Reciprocal is 1/time so you can set 1/125 on a shutter dial.

Exact formula

N = 16. t = (1/ISO) / 2^conditionStops. Reciprocal = 1/t. ConditionStops: +1 sand/snow, 0 sun, −1 slight overcast, −2 overcast, −3 heavy. Limits: Latitude, time of day, polarizer, shade under trees and mixed cloud omitted.

Looney 11

Full moon is roughly f/11 at 1/ISO, not f/16. Eclipses are much darker — use the lunar eclipse calculator, not sunny 16.

Open shade

Open shade is about four stops under sun (f/4 in the classic table), past the −3 heavy-overcast option here. Faces under a tree are not sunny 16 even if the park is in sun — meter them.

Frequently asked questions

Can I use f/8 instead of f/16?

Yes — that is two stops more aperture, so halve the shutter time twice (ISO 100: 1/400 instead of 1/100). This calculator stays on f/16 and only moves shutter with sky condition. Shift aperture separately if you want.

Why not open up for snow?

Snow and sand reflect extra light. The classic rule stops down or speeds the shutter so the whites stay white. Opening up is how you blow the highlights.

Film vs digital?

Same starting point. Digital has a histogram, so you can refine in one test shot. Negative film likes a bit more exposure; slide film likes this number or a hair under.

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