Phot to Lux Conversion Table
| Phot (ph) | Lux (lx) | Reference Benchmark | Formula Step |
|---|---|---|---|
| 0.0001 ph | 1 lx | Emergency exit pathway illumination minimum | 0.0001 × 10,000 = 1 lx |
| 0.001 ph | 10 lx | Residential hallway and twilight ambient light | 0.001 × 10,000 = 10 lx |
| 0.005 ph | 50 lx | Residential living room ambient illumination | 0.005 × 10,000 = 50 lx |
| 0.01 ph | 100 lx | Commercial stairwell and warehouse bulk aisle | 0.01 × 10,000 = 100 lx |
| 0.02 ph | 200 lx | General dining room and school classroom lighting | 0.02 × 10,000 = 200 lx |
| 0.03 ph | 300 lx | Library reading room and hotel conference workspace | 0.03 × 10,000 = 300 lx |
| 0.05 ph | 500 lx | Standard commercial office computer desktop | 0.05 × 10,000 = 500 lx |
| 0.075 ph | 750 lx | Technical drawing board and precision inspection desk | 0.075 × 10,000 = 750 lx |
| 0.1 ph | 1000 lx | Precision electronic assembly and watchmaking bench | 0.1 × 10,000 = 1,000 lx |
| 0.2 ph | 2000 lx | Hospital surgical operating theater task field | 0.2 × 10,000 = 2,000 lx |
| 0.5 ph | 5000 lx | Television studio and film production set lighting | 0.5 × 10,000 = 5,000 lx |
| 1 ph | 10000 lx | Overcast overcast midday outdoor daylight baseline | 1 × 10,000 = 10,000 lx |
| 2.5 ph | 25000 lx | Full indirect daylight under clear blue sky | 2.5 × 10,000 = 25,000 lx |
| 5 ph | 50000 lx | Direct bright morning or afternoon sunlight | 5 × 10,000 = 50,000 lx |
| 10 ph | 100000 lx | Direct overhead tropical noon solar illumination | 10 × 10,000 = 100,000 lx |
| 13 ph | 130000 lx | Peak high-altitude alpine direct sunlight | 13 × 10,000 = 130,000 lx |
Phot to Lux Formula & Unit Definitions
The dimensional ratio between phot and lux is mathematically exact at 10,000. In CGS metric definitions: 1 cm² = 0.0001 m². Therefore, 1 phot = 1 lm / 0.0001 m² = 10,000 lm/m² = 10,000 lux. Multiplying any illuminance value in phot by 10,000 converts it directly to lux.
Quick Estimation: To convert phot to lux mentally, move the decimal point four places to the right (multiply by 10,000). For example, 0.05 phot on an office desk becomes 500 lux.
Phot (ph)
Source Unit- Centimetre-gram-second (CGS) photometric unit defined as 1 lumen per square centimeter (lm/cm²).
- Historically utilized in 20th-century optics, spectroscopy, and high-intensity lamp characterization.
- High-density scale where typical overcast daylight equals 1 ph and full direct sunlight is 10 to 13 ph.
Lux (lx)
Target Unit- Coherent International System of Units (SI) derived base unit of illuminance (lm/m²).
- Standard unit across architectural lighting codes, agricultural grow rooms, and workplace safety.
- Represents broad-area illuminance, equaling exactly 10,000 times the phot value.
Frequently Asked Questions
Q.How do you convert phot to lux accurately?
Multiply the illuminance in phot by 10,000. For instance, 0.05 phot multiplied by 10,000 yields exactly 500 lux.
Q.What is the exact mathematical ratio between phot and lux?
One phot equals exactly 10,000 lux because 1 square meter contains 10,000 square centimeters. Conversely, 1 lux equals exactly 0.0001 phot.
Q.What is the physical difference between Phot and Lux?
Phot is a historical CGS unit representing lumens per square centimeter (lm/cm²), while Lux is the coherent SI unit representing lumens per square meter (lm/m²).
Q.Why is 1 phot equal to 10,000 lux?
Because one square meter (1 m × 1 m) contains exactly 100 cm × 100 cm = 10,000 cm². Therefore, an illumination intensity of 1 lumen per cm² spreads across 10,000 lumens per m².