Photography Exposure API
Photographic exposure maths as an API, computed locally and deterministically — the exposure-value, equivalent-exposure and Sunny-16 numbers a photographer, camera-app developer or educator works the exposure triangle with. The exposure-value endpoint gives EV = log₂(aperture² ÷ shutter) and the ISO-100-normalised EV100 (subtracting log₂(ISO/100)) — every one-EV step is a stop, a doubling or halving of light — so bright sun reads about EV 15 and a typical interior EV 6–8, and equal-EV settings give the same exposure. The equivalent endpoint applies the reciprocity at the heart of the triangle: exposure ∝ shutter × ISO ÷ f-number², so when you close the aperture or drop the ISO it returns the new shutter that keeps the brightness constant — going from f/2.8 to f/5.6 needs four times the shutter time. The sunny16 endpoint gives the classic meterless rule: in bright sun shoot f/16 at about 1/ISO (1/125 s at ISO 100), opening up in stops for softer light — slight overcast f/11, overcast f/8, heavy overcast f/5.6, open shade f/4, and f/22 on snow or sand — solving the shutter for your chosen ISO and aperture. Everything is computed locally and deterministically, so it is instant and private. Ideal for camera and photography apps, exposure-calculator and teaching tools, and metering and automation utilities. Pure local computation — no key, no third-party service, instant. 3 compute endpoints. For depth of field and hyperfocal distance use a photography (optics) API.
api.oanor.com/exposure-api
