> light_source {<sun_x,sun_y,sun_z>
>               SpectralEmission(E_D80)
>               }
> My solar irradiance in 730nm is 1.33015.I should use E_D50 or E_D65 or
> E_D93.Should I choose which one is my need ?Help!
> http://en.wikipedia.org/wiki/Standard_illuminant#Illuminant_series_D

1.33015 @ 730 nm tells you the intensity of the light at a single 
wavelength (very deep red). It tells you nothing about the overall 
brightness of the light, or what the colour of that light is.

The "colour" of the light is determined by the relative intensity at all 
the different wavelengths (the shape of the spectrum), the brightness by 
a combination of the absolute intensity at every visible wavelength.

D50, D65 or D93 are standard distributions of wavelength intensities 
meant to represent different types of daylight, they don't say anything 
about "brightness".

You either need to go back to where you got the 1.33015 figure from and 
get the rest of the data for other wavelengths, or just pick one of the 
standard illuminants to use, D65 is quite commonly used.

By the way, the spectra for D65 etc are probably far more accurate in 
the middle of the visible spectrum (around 550 nm) that right at one 
edge (730 nm), so I wouldn't scale based on your value at 730 nm. If 
possible get the irradiance nearer 550 nm.

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