Lux to Phot Conversion Table
| Lux (lx) | Phot (ph) | Reference Benchmark | Formula Step |
|---|---|---|---|
| 1 lx | 0.0001 ph | Emergency exit pathway illumination minimum | 1 × 0.0001 = 0.0001 ph |
| 10 lx | 0.001 ph | Residential hallway and twilight ambient light | 10 × 0.0001 = 0.001 ph |
| 50 lx | 0.005 ph | Residential living room ambient illumination | 50 × 0.0001 = 0.005 ph |
| 100 lx | 0.01 ph | Commercial stairwell and warehouse bulk aisle | 100 × 0.0001 = 0.01 ph |
| 200 lx | 0.02 ph | General dining room and school classroom lighting | 200 × 0.0001 = 0.02 ph |
| 300 lx | 0.03 ph | Library reading room and hotel conference workspace | 300 × 0.0001 = 0.03 ph |
| 500 lx | 0.05 ph | Standard commercial office computer desktop | 500 × 0.0001 = 0.05 ph |
| 750 lx | 0.075 ph | Technical drawing board and precision inspection desk | 750 × 0.0001 = 0.075 ph |
| 1000 lx | 0.1 ph | Precision electronic assembly and watchmaking bench | 1,000 × 0.0001 = 0.1 ph |
| 2000 lx | 0.2 ph | Hospital surgical operating theater task field | 2,000 × 0.0001 = 0.2 ph |
| 5000 lx | 0.5 ph | Television studio and film production set lighting | 5,000 × 0.0001 = 0.5 ph |
| 10000 lx | 1 ph | Overcast overcast midday outdoor daylight baseline | 10,000 × 0.0001 = 1 ph |
| 25000 lx | 2.5 ph | Full indirect daylight under clear blue sky | 25,000 × 0.0001 = 2.5 ph |
| 50000 lx | 5 ph | Direct bright morning or afternoon sunlight | 50,000 × 0.0001 = 5 ph |
| 100000 lx | 10 ph | Direct overhead tropical noon solar illumination | 100,000 × 0.0001 = 10 ph |
| 130000 lx | 13 ph | Peak high-altitude alpine direct sunlight | 130,000 × 0.0001 = 13 ph |
Lux to Phot Formula & Unit Definitions
The mathematical ratio is derived directly from metric area definitions: 1 meter equals 100 centimeters, so 1 square meter equals (100 cm)² = 10,000 square centimeters. Since 1 lux = 1 lm / 10,000 cm² = 0.0001 lm/cm², 1 lux equals exactly 0.0001 phot. Dividing any lux measurement by 10,000 (or multiplying by 0.0001) gives its exact equivalent in phot.
Quick Estimation: To convert lux to phot in your head, move the decimal point four places to the left (divide by 10,000). For example, direct overhead sunlight at 100,000 lux converts to 10 phot.
Lux (lx)
Source Unit- Coherent SI derived unit of illuminance defined as 1 lumen per square meter (lm/m²).
- Universal worldwide standard for architectural lighting, environmental monitoring, and safety codes.
- Measures wide-area illumination where full indirect daylight corresponds to roughly 10,000 to 25,000 lx.
Phot (ph)
Target Unit- Centimetre-gram-second (CGS) unit of illuminance defined as 1 lumen per square centimeter (lm/cm²).
- Historically standard in early optical physics, astrophysics, and photolithography.
- Represents 10,000 times higher luminous intensity per unit area than lux, where 1 ph equals 10,000 lx.
Frequently Asked Questions
Q.How do you convert lux to phot accurately?
Multiply the illuminance in lux by 0.0001 (or divide by 10,000). For instance, 10,000 lux divided by 10,000 equals exactly 1 phot.
Q.What is the exact mathematical ratio between lux and phot?
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 Lux and Phot?
Lux is the modern SI coherent unit representing lumens per square meter (lm/m²), while Phot is a CGS metric unit representing lumens per square centimeter (lm/cm²).
Q.Is phot still used in modern lighting engineering?
While modern architectural lighting exclusively uses lux and foot-candles, the phot remains relevant in optical sensor engineering, historic physics papers, and photolithography.