Illumination / fc → ph
Convert Foot-candles to Phot
Convert illuminance on a surface between lux and foot-candles. Convert Foot-candles (fc) to Phot (ph). Find the formula, worked examples, unit definitions, and practical guidance below.
Reverse: Phot to Foot-candles →
How to convert foot-candles to phot
Illuminance is luminous flux per area, not radiant watts per area. One lux is one lumen per square meter. Photometric weighting prevents a universal lux-to-watts conversion.
Use x for the value in fc, b for the intermediate value in lx, and y for the result in ph.
ph = fc × 10.763910416709722 ÷ 10000
Worked examples
10 fc ≈ 0.0107639104167 ph
Step 1: (10 × 10.7639104167) ≈ 107.639104167 lx.
Step 2: 107.639104167 ÷ 10000 ≈ 0.0107639104167 ph.20 fc ≈ 0.0215278208334 ph
Step 1: (20 × 10.7639104167) ≈ 215.278208334 lx.
Step 2: 215.278208334 ÷ 10000 ≈ 0.0215278208334 ph.
Results are rounded to 12 significant digits. Converting units does not increase the precision of the original measurement. Very large or small values outside JavaScript’s finite numeric range are rejected.
About Foot-candles
Foot-candles (fc) measures illumination under the conventions above. The base value in lx is (x × 10.7639104167), where x is the numerical value in fc. Factors shown here are rounded for display; calculations use the stored factor.
About Phot
Phot (ph) measures illumination under the conventions above. The base value in lx is (x × 10000), where x is the numerical value in ph. Factors shown here are rounded for display; calculations use the stored factor.
Definitions and sources
Carry the same physical assumptions into subsequent physics calculations.
Foot-candles to phot reference table
| Foot-candles (fc) | Phot (ph) |
|---|---|
| 1 | 0.00107639104167 |
| 5 | 0.00538195520835 |
| 10 | 0.0107639104167 |
| 25 | 0.0269097760418 |
| 50 | 0.0538195520835 |
| 100 | 0.107639104167 |
| 1000 | 1.07639104167 |
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