Troland
The troland (symbol Td), named after Leonard T. Troland, is a unit of conventional retinal illuminance. It is meant as a method for correcting photometric measurements of luminance values impinging on the human eye by scaling them by the effective pupil size. It is equal to retinal illuminance produced by a surface whose luminance is one nit when the apparent area of the entrance pupil of the eye is 1 square milimeter. [1]
The troland typically refers to the ordinary or photopic troland, which is defined in terms of the photopic luminance:
where L is the photopic luminance in cd m-2 and p is pupil area in mm2
A scotopic troland is also sometimes defined:
where L′ is the scotopic luminance in cd m-2 and p is pupil area in mm2
Conversions to other units
| 1 troland | 10 kcd/m^2 (kilocandelas per square meter) |
| 10000 cd/m^2 (candelas per square meter) | |
| 1×10^7 mcd/m^2 (millicandelas per square meter) | |
| 1×10^10 mucd/m^2 (microcandelas per square meter) | |
| 1 cd/cm^2 (candela per square centimeter) | |
| 3.142 La (lamberts) (unit officially deprecated) | |
| 2919 footlamberts (unit officially deprecated) | |
| 2919 equivalent foot-candles (unit officially deprecated) | |
| 31416 blondels (unit officially deprecated) | |
| 10000 nit (nits) (unit officially deprecated) | |
| 3.142×10^7 skots (unit officially deprecated) | |
| 1 stilb (unit officially deprecated) |
Conversions from Other Units
| 1 kcd/m^2 | 0.1 trolands |
| 1 cd/m^2 | 1×10^-4 trolands |
| 1 mcd/m^2 | 1×10^-7 trolands |
| 1 mucd/m^2 | 1×10^-10 trolands |
| 1 cd/cm^2 | 1 troland |
| 1 La | 0.3183 trolands |
| 1 footlambert | 3.426×10^-4 trolands |
| 1 equivalent foot-candle | 3.426×10^-4 trolands |
| 1 blondel | 3.183×10^-5 trolands |
| 1 nit | 1×10^-4 trolands |
| 1 skot | 3.183×10^-8 trolands |
| 1 stilb | 1 troland |
Physical quantities
- luminance
- equivalent luminance [2]
Unit system
centimeter-gram-second (cgs) [2]
Unit status
officially deprecated [2]
Basic unit dimensions
[length]^(-2) [luminous intensity] [2]
Comparisons
- ≈ 0.8 × luminance of a kerosene candle (≈ 12000 cd/m^2 )
- ≈ luminance of a sperm candle (≈ 10000 cd/m^2 )
- ≈ luminance of an average daytime clear sky (≈ 8000 cd/m^2 )[2]