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The '''troland''' (symbol '''Td'''), named after [[Leonard T. Troland]], is a unit of ''conventional retinal illuminance''. It is meant as a method for correcting [[photometry (optics)|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 (unit)|nit]] when the apparent area of the entrance pupil of the eye is 1 square milimeter. <ref> [http://www.answers.com/topic/troland answers.com]</ref> | |||
The troland typically refers to the ordinary or [[photopic]] troland, which is defined in terms of the photopic luminance: | |||
:<math> \mathrm{T} = \mathrm{L} \times \mathrm{p} </math> | |||
where ''L'' is the photopic luminance in [[candela|cd]] [[square metre|m<sup>-2</sup>]] and ''p'' is pupil area in mm<sup>2</sup> | |||
A [[scotopic]] troland is also sometimes defined: | |||
:<math> \mathrm{T'} = \mathrm{L'} \times \mathrm{p} </math> | |||
where ''L′'' is the scotopic luminance in [[candela|cd]] [[square metre|m<sup>-2</sup>]] and ''p'' is pupil area in mm<sup>2</sup> | |||
== Conversions to other units== | |||
{| class="wikitable" | |||
|- | |||
| 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) | |||
|} <ref name=wolframalpha.com>[http://www.wolframalpha.com/input/?i=troland wolframalpha.com] </ref> | |||
==Conversions from Other Units== | |||
{| class="wikitable" | |||
|- | |||
|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 | |||
|} <ref name=wolframalpha.com /> | |||
==Physical quantities== | |||
* luminance | |||
*equivalent luminance <ref name=wolframalpha.com /> | |||
==Unit system== | |||
centimeter-gram-second (cgs) <ref name=wolframalpha.com /> | |||
==Unit status== | |||
officially deprecated <ref name=wolframalpha.com /> | |||
==Basic unit dimensions== | |||
[length]^(-2) [luminous intensity] <ref name=wolframalpha.com /> | |||
==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 )<ref name=wolframalpha.com /> | |||
==See also== | |||
*[[Leonard T. Troland]] | |||
*[[Troland Research Awards]] | |||
==References== | |||
{{reflist}} | |||
[[Category:Photometry]] | |||
[[Category:Vision]] | |||
[[Category:Non-SI metric units]] | |||
[[Category:Units of illuminance]] | |||
Revision as of 00:53, 26 October 2013
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]
See also
References
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