Photometric & Optics
Candela Distribution Calculator
Visualize luminous intensity distribution patterns across angles. Select a distribution type and adjust intensity to see the polar plot update in real time.
Distribution Type
Peak Intensity 1000 cd
Lambertian: Ideal diffuse emitter. Intensity proportional to cos(θ). Equal luminance from all viewing angles. Typical of matte white surfaces and bare LED chips.
1000
cd
Peak Intensity
120°
Beam Angle
50% intensity (FWHM)
180°
Field Angle
10% intensity cutoff
Intensity by Angle
| Angle (°) | Intensity (cd) | % of Peak | Zone |
|---|
Candela vs lumens — what’s the difference?
Lumens (lm)
The total light a source emits in every direction — the size of the bucket of light.
Candela (cd)
Light intensity in one direction — how concentrated that light is where you aim it.
Same lumens, different optic: squeeze the light into a narrow beam and candela shoots up (a bright, tight pool); spread it wide and candela drops (a soft, dim wash). That’s why a 1000 lm spotlight and a 1000 lm floodlight feel completely different even though they emit the same total light.
Lumens → peak candela
I = Φ / Ω · Ω = 2π (1 − cos(θ / 2))
I = candela Φ = lumens Ω = solid angle (steradians)
I = candela Φ = lumens Ω = solid angle (steradians)
Drag the beam angle down and watch the same lumens produce far higher candela — that spike is beam concentration, the whole point of a spot optic. (Assumes an even beam; real optics vary.)
Distribution types & where they’re used
| Distribution | Real-world use |
|---|---|
| Narrow, high candela | Accent lighting, artwork, spotlights |
| Medium | Retail & display |
| Wide | Ambient & general room lighting |
| Batwing | Open offices, uniform spacing |
| Asymmetric | Wall washing, signage, facades |
Quick glossary
- CBCP — center beam candlepower
- The candela measured straight down the middle of the beam: its peak intensity.
- Beam angle
- The cone where intensity is at least 50% of peak (also called FWHM).
- Field angle
- The wider cone where intensity is at least 10% of peak.
- Candela vs lux
- Candela is intensity at the source; lux is what lands on a surface — lux = candela ÷ distance².