direct sun - through thin high cirrus cloud
6.5 UVI = 5.5
6.2 UVB = 260
luxmeter = 85,700
Spectrum 338: SUN EditDelete
|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||( 0.32 ; 0.32 )||( 0.4 ; 0.39 )||( 0.26 ; 0.29 ; 0.29 )|
|CCT||6200 Kelvin||5000 Kelvin||5500 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) 4650 µW/cm² = 46.5 W/m² UVA (US) ( 320 nm - 400 nm) 4560 µW/cm² = 45.6 W/m² UVB (EU) ( 280 nm - 315 nm) 95.1 µW/cm² = 0.951 W/m² UVB (US) ( 280 nm - 320 nm) 186 µW/cm² = 1.86 W/m² UVC ( 0 nm - 280 nm) 0 µW/cm² = 0 W/m² vis. UVA ( 350 nm - 380 nm) 1900 µW/cm² = 19 W/m² purple ( 380 nm - 420 nm) 4220 µW/cm² = 42.2 W/m² blue ( 420 nm - 490 nm) 11900 µW/cm² = 119 W/m² green ( 490 nm - 575 nm) 12400 µW/cm² = 124 W/m² yellow ( 575 nm - 585 nm) 1450 µW/cm² = 14.5 W/m² orange ( 585 nm - 650 nm) 9300 µW/cm² = 93 W/m² red ( 650 nm - 780 nm) 14200 µW/cm² = 142 W/m² VIS ( 380 nm - 780 nm) 53500 µW/cm² = 535 W/m² PAR ( 400 nm - 700 nm) 44100 µW/cm² = 441 W/m² total ( 0 nm - 0 nm) 61000 µW/cm² = 610 W/m² UVA1 ( 315 nm - 350 nm) 1270 µW/cm² = 12.7 W/m² VIS Rep3 ( 350 nm - 600 nm) 34000 µW/cm² = 340 W/m² VIS Rep4 ( 350 nm - 700 nm) 47500 µW/cm² = 475 W/m² IRA ( 700 nm - 1400 nm) 12100 µW/cm² = 121 W/m² IRB ( 1400 nm - 3000 nm) 0 µW/cm² = 0 W/m²
Erythema 4.7 UV-Index Pyrimidine dimerization of DNA 66.5 µW/cm² Photoceratitis 6.45 µW/cm² Photoconjunctivitis 0.0585 µW/cm² DNA Damage 0.176 Vitamin D3 18.7 µW/cm² Photosynthesis 31800 µW/cm² Luminosity 113000 lx Human L-Cone 16800 µW/cm² Human M-Cone 14000 µW/cm² Human S-Cone 9640 µW/cm² CIE X 15700 µW/cm² CIE Y 15500 µW/cm² CIE Z 17900 µW/cm² PAR 208000000 mol photons Extinction preD3 0.192 m²/mol Extinction Tachysterol 0.71 m²/mol Extinction Lumisterol 0.0101 m²/mol Extinction 7DHC 0.00408 m²/mol L-Cone 14400 µW/cm² M-Cone 16000 µW/cm² S-Cone 15900 µW/cm² U-Cone 8430 µW/cm² UVR - ICNIRP 2004 2.62 Rel Biol Eff Melatonin Supression 14400 µW/cm² Blue Light Hazard 11000 µW/cm² (98.1 µW/cm² per 1000 lx) CIE 174:2006 PreVit D3 20.6 µW/cm² Lumen Reptil 126000 "pseudo-lx" Vitamin D3 Degradation 38.8 µW/cm²
Solarmeter 6.2 (UVB, pre 2010) 272 µW/cm² Solarmeter 6.5 (UV-Index, pre 2010) 5.94 Leybold UVB 176 µW/cm² Leybold UVA 2320 µW/cm² Leybold UVC 0 µW/cm² DeltaOhm UVB 666 µW/cm² DeltaOhm UVC 64.4 µW/cm² Vernier UVB 43.2 µW/cm² Vernier UVA 1670 µW/cm² Gröbel UVA 2580 µW/cm² Gröbel UVB 77.7 µW/cm² Gröbel UVC -0.0511 µW/cm² Solarmeter 6.4 (D3) 18.6 IU/min UVX-31 796 µW/cm² IL UVB 0.132 µW/cm² IL UVA 2720 µW/cm² Solarmeter 6.5 (UVI, post 2010) 5.31 UV-Index Solarmeter 6.2 (UVB, post 2010) 200 µW/cm² (Solarmeter Ratio = 37.7) Solarmeter AlGaN 6.5 UVI sensor 84.3 UV Index GenUV 7.1 UV-Index 5.78 UV-Index Solarmeter 10.0 (Global Power) 676 W/m² Solarmeter 4.0 (UVA) 45.8 mW/cm²