Metering without a meter: Sunny 16 at the shore
In full sun, set the aperture to f/16 and the shutter to one over the film speed. A 400-speed film gets 1/500 s at f/16, a 125-speed film 1/125 s. Every other condition is a number of stops away from that, and the list of conditions is short enough to memorise.
| Light | Shadows look | Aperture at 1/ISO |
|---|---|---|
| Sun on sand, snow or open water | Hard, very dark | f/22 |
| Bright sun | Sharp-edged | f/16 |
| Hazy sun | Soft-edged | f/11 |
| Bright overcast | Barely visible | f/8 |
| Heavy overcast | None | f/5.6 |
| Open shade, or the hour after sunrise | None | f/4 |
Why the beach is different
Pale sand and water throw a stop of extra light back up into the scene, which is why the first row exists. A meter pointed at the same scene is fooled in the other direction: it sees all that brightness, assumes the world is mid-grey, and gives a reading that turns white surf into grey porridge. Here the rule is more reliable than the instrument.
Negative film forgives one way
Black-and-white negative film tolerates two stops of overexposure with nothing worse than a dense negative, and less than one stop of underexposure before the shadows empty. When unsure between two rows of the table, take the lower one. The old advice to expose for the shadows and let development take care of the highlights is the same idea said more grandly.
Past the bottom of the table
The rule runs out at dusk, where a stop of light goes every few minutes and the eye adapts fast enough to hide it. A few fixed points help.
| Scene | At ISO 100, f/8 |
|---|---|
| Ten minutes after sunset, clear sky | 1/15 s |
| Twenty minutes after sunset | 1 s |
| Thirty minutes after, horizon still glowing | 8 s |
| Harbour lights, sky nearly dark | 30 s |
| Full moon on the water, no other light | 4 min |
All of these are before the film's own correction for long times, which at eight seconds already adds a stop on most traditional emulsions. Bracket towards more exposure, never less.
Practice
Guess before every meter reading for a month and write both down. By the end the guess is within half a stop nine times out of ten, and the meter can stay in the bag on the days when the battery has died in the cold, which near the sea is most days in January.