Solar altitude 16.1° Puerto Rico,
Gran Canaria (Latitude 27°47'N,
June 19th 2011 Local time 08:30h
Spectrum 511: SUN EditDelete
Solar altitude 16.1° Puerto Rico,
|Ballast||- no ballast or default/unknown ballast -|
|Originator (measurement)||Frances Baines|
Colorimetry is the science to describe physically the human color perception. The wavelength range 380 nm - 780 nm is visible to humans and detected by three different photoreceptors. Many Reptiles see the range 350 nm - 800 nm and have an additional UV photoreceptor in their retina.
Whereas a spectrometer measures the intensity in every tiny wavelength interval resulting in thousands of individual intensities, the human eye only measures three intensities detected by the three cones. The same is true for the reptile eye with usually three or four photoreceptors. Effectively the detailled spectrum displayed above reduces to a much compacter bar graph displayed below. The photoreceptor sensitivites from these L-Cone, M-Cone, S-Cone, and U-Cone are used, they are chosen as an average of measured reptile photoreceptor sensitivity curves. The bar graph also shows as reference the intensity seen by the three or four photoreceptors for average sunlight (id 1).
From these three numbers the colour coordinate and the correlated colour temperature for humans are calculated using the CIE standard method. I adapted this concept to a "3 cone reptile (M,S,U)" and a "4 cone reptile (L,M,S,U)". I am sure, that this adaption to other colour spaces makes sense mathematically and this is also done in scientific research regarding colour vision of animals, however I have not seen calculation of colour temperatures for other animals in the scientific literature. Even if it is hypothetical, at least this shows, how arbitrary the colour temperature is, and that the colour temperature calculated for humans does not apply to reptiles. The colour spaces also show the colour coordinates of different phases of daylight ((ids 1, 338 – 451, 511 – 513 ), indicated by crosses, coloured in the appriximate colour perceived by a human.
|Human (CIE)||3 cone reptile||4 cone reptile|
|Colour Coordinate||( 0.29 ; 0.28 )||( 0.34 ; 0.42 )||( 0.21 ; 0.27 ; 0.33 )|
|CCT||9700 Kelvin||6200 Kelvin||7000 Kelvin|
|colour space||3-D-graph not implemented yet|
Vitamin D3 is produced by UVB radiation around 300 nm. 7DHC/ProD3 present in the skin is converted to PreD3 when absorbing an UV photon. PreD3 can be converted back to ProD3, to Lumisterol, or to Tachysterol when absorbing another UV photon or can be converted to Vitamin D3 in a warm environment.
The equilibrium of the photoproducts depends on the actual UV spectrum in the range 250 nm - 340 nm. With knowledge of the conversion probabilities and absorption spectra of 7DHC, PreD3, Tachysterol, and Lumisterol it is possible to calculate the ratio of photoproducts in equilibrium. This is based on scientific literature , however the constants that are used for the calculation are not well calibrated with experiments. It is therefore not a solid method, but I consider it useful as a first guess how natural a UV spectrum is.
Caveat: This evaluation is extremely sensitive to the qualitiy of the spectral measurement in the range 220 nm - 340 nm. High quality spectrometers and good background calibration is needed to get the noise below 300 nm low enough for this evaluation. Please check at least the UV graph above for noise.
The ratio of the two solarmeters 6.2 (UVB) and 6.5 (UV index) readings has proven a useful and very simply number to acess the spectral shape in the vitamin-d3-active region.
The calculation method is a numerical implementation (Simpson's rule) of the formula
To learn more about calculating effective irradiances and radiometers I recommend this excellent report on UVB meters: Characterizing the Performance of Integral Measuring UV-Meters (pdf).
The numbers in the following tables can also be used to estimate certain (effective) irradiances from radiomer readings. Example: If the database lists
- range: UVB (US) = 13.8 µW/cm²
- radiometer: Solarmeter 6.2 = 19.6 µW/cm²
UVA (EU) ( 315 nm - 400 nm) 422 µW/cm² = 4.22 W/m² UVA (US) ( 320 nm - 400 nm) 417 µW/cm² = 4.17 W/m² UVB (EU) ( 280 nm - 315 nm) 2.71 µW/cm² = 0.0271 W/m² UVB (US) ( 280 nm - 320 nm) 8.17 µW/cm² = 0.0817 W/m² UVC ( 0 nm - 280 nm) 0 µW/cm² = 0 W/m² vis. UVA ( 350 nm - 380 nm) 175 µW/cm² = 1.75 W/m² purple ( 380 nm - 420 nm) 376 µW/cm² = 3.76 W/m² blue ( 420 nm - 490 nm) 934 µW/cm² = 9.34 W/m² green ( 490 nm - 575 nm) 742 µW/cm² = 7.42 W/m² yellow ( 575 nm - 585 nm) 81 µW/cm² = 0.81 W/m² orange ( 585 nm - 650 nm) 499 µW/cm² = 4.99 W/m² red ( 650 nm - 780 nm) 719 µW/cm² = 7.19 W/m² VIS ( 380 nm - 780 nm) 3350 µW/cm² = 33.5 W/m² PAR ( 400 nm - 700 nm) 2830 µW/cm² = 28.3 W/m² total ( 0 nm - 0 nm) 4060 µW/cm² = 40.6 W/m² UVA1 ( 315 nm - 350 nm) 116 µW/cm² = 1.16 W/m² VIS Rep3 ( 350 nm - 600 nm) 2420 µW/cm² = 24.2 W/m² VIS Rep4 ( 350 nm - 700 nm) 3140 µW/cm² = 31.4 W/m² IRA ( 700 nm - 1400 nm) 798 µW/cm² = 7.98 W/m² IRB ( 1400 nm - 3000 nm) 0 µW/cm² = 0 W/m²
Erythema 0.183 UV-Index Pyrimidine dimerization of DNA 2.56 µW/cm² Photoceratitis 0.14 µW/cm² Photoconjunctivitis 0.00045 µW/cm² DNA Damage 0.00248 Vitamin D3 0.353 µW/cm² Photosynthesis 2090 µW/cm² Luminosity 6580 lx Human L-Cone 973 µW/cm² Human M-Cone 840 µW/cm² Human S-Cone 773 µW/cm² CIE X 941 µW/cm² CIE Y 903 µW/cm² CIE Z 1420 µW/cm² PAR 13100000 mol photons Extinction preD3 0.00877 m²/mol Extinction Tachysterol 0.0354 m²/mol Extinction Lumisterol 0.000107 m²/mol Extinction 7DHC 2.27E-5 m²/mol L-Cone 811 µW/cm² M-Cone 1060 µW/cm² S-Cone 1310 µW/cm² U-Cone 756 µW/cm² UVR - ICNIRP 2004 0.0943 Rel Biol Eff Melatonin Supression 1100 µW/cm² Blue Light Hazard 891 µW/cm² (135 µW/cm² per 1000 lx) CIE 174:2006 PreVit D3 0.326 µW/cm² Lumen Reptil 8670 "pseudo-lx" Vitamin D3 Degradation 2.01 µW/cm²
Solarmeter 6.2 (UVB, pre 2010) 15.7 µW/cm² Solarmeter 6.5 (UV-Index, pre 2010) 0.165 Leybold UVB 9.06 µW/cm² Leybold UVA 217 µW/cm² Leybold UVC 0 µW/cm² DeltaOhm UVB 52.1 µW/cm² DeltaOhm UVC 4.31 µW/cm² Vernier UVB 0.941 µW/cm² Vernier UVA 151 µW/cm² Gröbel UVA 238 µW/cm² Gröbel UVB 3.48 µW/cm² Gröbel UVC -0.00296 µW/cm² Solarmeter 6.4 (D3) 0.517 IU/min UVX-31 64.1 µW/cm² IL UVB 0.00881 µW/cm² IL UVA 252 µW/cm² Solarmeter 6.5 (UVI, post 2010) 0.15 UV-Index Solarmeter 6.2 (UVB, post 2010) 12.8 µW/cm² (Solarmeter Ratio = 85.5) Solarmeter AlGaN 6.5 UVI sensor 2.71 UV Index GenUV 7.1 UV-Index 0.263 UV-Index Solarmeter 10.0 (Global Power) 43.2 W/m² Solarmeter 4.0 (UVA) 4.18 mW/cm²