Disparai — Camera Exposure and Sunny 16 | disparai.com
An ordered procedure for setting ISO, aperture and shutter speed in full sun, shade and the two common failure cases.
Step 1 — Set the ISO. Choose the film speed or the sensor setting before anything else, because the shutter speed the rule gives you is the reciprocal of that number. With ISO 100 film the rule gives 1/100 of a second at f/16; with ISO 400 film it gives 1/400 s, usually set as 1/500 s on a camera with a conventional shutter dial.
Step 2 — Set the aperture to f/16 in full sun. Look at the shadows: distinct hard shadows mean full sun and f/16. Soft, open shadows mean one step wider at f/11. Barely visible shadows mean f/8. No shadows at all mean f/5.6 or wider. The sunny 16 rule says that on a sunny day, at an aperture of f/16, a suitable shutter speed is one over the film speed.
Step 3 — Set the shutter to one over the ISO. With the aperture fixed, set the shutter to the reciprocal of the ISO and take the shot. If your camera's dial does not have the exact marking, use the nearest one; half a stop of error is invisible on film and negligible on a sensor.
On narrow screens, swipe or scroll the plate sideways.
Step 4 — Adjust for shade. Open the aperture one step and double the shutter time for each step of cloud cover. From f/16 at 1/100 s in full sun, move to f/11 at 1/50 s in light shade, f/8 at 1/25 s in open shade, f/5.6 at 1/15 s in deep shade or under heavy overcast.
Failure mode — backlit subject. If the sun is behind your subject, the face in front of the lens receives roughly two stops less light than the meter reading of the bright background suggests. Open the aperture two steps from f/16 to f/8, use a fill flash, or accept a deliberate silhouette.
Failure mode — snow and light sand. Bright snow reflects far more light than mid-grey, so a meter aimed at it will underexpose by one to two stops. The EV table already accounts for this: EV 16 for light sand or snow against EV 15 for a typical full-sun scene. Exposing for EV 16 keeps the snow white rather than grey.
Further reading