Illuminance Converter
Foot-candle (fc)
Definition: A foot-candle (symbol: fc, lm/ft², or ft-c) is a non-SI unit of illuminance used primarily in the United States customary system. It is defined as one lumen per square foot.
History/origin: Historically, it was defined as the illuminance produced on a surface by a standard "spermace candle" (a candle made from whale oil) at a distance of exactly one foot. It was the common unit before metric standardization.
Current use: Foot-candles are still widely used in the United States and the UK by architects, cinematographers, photographers, and stage lighting designers to set up optimal lighting environments.
Phot (ph)
Definition: A phot (symbol: ph) is a unit of illuminance in the older CGS (centimeter-gram-second) system. It is defined as one lumen per square centimeter, making it equivalent to 10,000 lux.
History/origin: The unit was formulated in the early 20th century as part of the CGS metric system. The name derives from the Greek word "phos," meaning light.
Current use: The phot is largely obsolete today, having been replaced by the SI unit Lux. However, it is still occasionally found in older scientific literature or highly specific physics applications.
Foot-candle (fc) to Phot (ph) Conversion Table
| Foot-candle (fc) [fc] | Phot (ph) [ph] |
|---|---|
| 0.01 fc | 0.00001076 ph |
| 0.1 fc | 0.00010764 ph |
| 1 fc | 0.00107639 ph |
| 2 fc | 0.00215278 ph |
| 3 fc | 0.00322917 ph |
| 5 fc | 0.00538196 ph |
| 10 fc | 0.01076391 ph |
| 20 fc | 0.02152782 ph |
| 50 fc | 0.05381955 ph |
| 100 fc | 0.1076391 ph |
| 1000 fc | 1.07639104 ph |
How to Convert Foot-candle (fc) to Phot (ph)
1 fc = 0.00107639 ph
1 ph = 929.03040144 fc
Example: convert 15 fc to ph:
15 fc = 15 × 0.00107639 ph = 0.01614587 ph
Did You Know?
- The term "Foot-candle" is completely literal! Historically, it was defined as the exact amount of light cast by a single standard candle onto a surface exactly one foot away.
- A Phot (ph) is an extremely bright unit of measurement. Just one Phot is equal to 10,000 Lux, which is roughly equivalent to the lighting used in professional TV broadcasting studios.