#illuminance

Photometry and lighting maths as an API, computed locally and deterministically. The illuminance endpoint computes the light falling on a surface from a point source, E = I·cos(θ)/d² in lux, from the luminous intensity in candela, the distance in metres and the angle of incidence from the surface normal — a 1000 cd source straight down at 2 m gives 250 lux. The inverse-square endpoint scales a known illuminance to a new distance, E2 = E1·(d1/d2)², so doubling the distance quarters the light. The flux-intensity endpoint converts between luminous flux in lumens and luminous intensity in candela through the solid angle, I = Φ/Ω and Φ = I·Ω, with the solid angle taken as the full sphere 4π steradian for an isotropic source or, for a spotlight of full beam angle β, Ω = 2π·(1 − cos(β/2)) — so a 100 cd isotropic source emits about 1256.6 lm, and a 1000 cd lamp in a 30° beam emits about 214 lm. Distances are in metres and angles in degrees. Everything is computed locally and deterministically, so it is instant and private. Ideal for lighting-design, architecture, photography, film, horticulture-grow-light, stage and AV app developers, lux-and-lumen and luminaire-planning tools, and engineering software. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. These are photometric (perceived-light) quantities; for blackbody/peak-wavelength radiometry use a Wien/radiation API.

api.oanor.com/photometry-api

Lighting design maths as an API, computed locally and deterministically. The room endpoint works out how many lumens a room needs from its area and a target illuminance — given directly in lux or chosen from a room-type preset (living, kitchen, office, workshop and more) — and, optionally, how many fixtures at a given lumen output and how many watts at a given lamp type. The lux endpoint converts between lux, footcandles and lumens over an area, so you can find the illuminance from a light output and a room size or vice versa. The efficacy endpoint relates lumens, watts and luminous efficacy (lumens per watt): give any two — or a lamp-type preset such as incandescent, halogen, CFL or LED — and it computes the third. Everything is computed locally and deterministically, so it is instant and private. It is a lumen-method estimate: target levels are typical guidance (EN 12464 / IES) and a full design would add room and utilisation factors. Ideal for lighting and electrical tools, interior-design and home apps, retrofit and energy-saving calculators, and smart-home planning. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is illumination maths; for Ohm's-law electrical quantities use an electronics API.

api.oanor.com/lighting-api