scott <sco### [at] scottcom> wrote:
> > I have known the value of solar irradiance in 817nm band is 1.08279
> > W/(m2*nm).How can I define it?
>
> 817nm is on the verge of not being visible at all to humans, you can
> look up the XYZ colour value of it from here:
>
> http://www.cvrl.org/database/data/cienewxyz/lin2012xyz10e_5_7sf.htm
>
> XYZ=(3.815429E-06,1.523114E-06,0.000000E+00)
>
> Compare the size of those numbers to the ones around 500 nm, they are tiny.
>
> If you want a realistic image output in sRGB then you can easily convert
> the XYZ values to RGB.
>
> Wikipedia has the matrix equation here:
>
>
http://en.wikipedia.org/wiki/SRGB#The_forward_transformation_.28CIE_xyY_or_CIE_XYZ_to_sRGB.29
>
> That will give you linear RGB which POV will accept with the "rgb"
> keyword, there is no need to do the second step for gamma correction
> (although you could if you wanted and then pass the values to POV with
> the "srgb" keyword, the results should be identical).
>
> > "light_source {<sun_x,sun_y,sun_z> color rgb
> > 1.08279 } "I set statement as above in pov,but I doublt it is wrong,because
> > 1.08279 is a solar irradiance,color rgb is color ，but I donnot know how
> > to convert them or how to define solar irradiance.beg a hot to help me !thank
> > you!
>
> The "scale" of lighting in the scene is up to you, a bit like the
> exposure of a camera. I suspect with a 817nm light source you'll need to
> multiply up the brightness by a large amount to get anything visible though.


> I have used "XYZ=(3.815429E-06,1.523114E-06,0.000000E+00)" ,then converted xyz > to
linear RGB in your help.I set  "l
ight_source {<sun_x,sun_y,sun_z> color
> rgb <1.00229e-005,3.46021e-006,-5.65828e-007> ,and set output file type to be
>"*.HDR".The first column is the value 
of each pixel in the hdr image which is >simulated by pov ；The second column is
the value of each pixel in my >r
eflection image which is real image.My goal is the hdr image which I simulated >equal
to my reflection image.But I find
 my real image is 10 times as hdr >image.The trend of this two image is same,only
having a 10 times between >them.So I 
think there must be have some relation in it.
        0.021973        0.220900
        0.037354        0.375800
        0.037354        0.375800
        0.034424        0.346500
        0.027710        0.277700
        0.035400        0.355800
        0.039551        0.396900
        0.043945        0.441800
        0.044189        0.442800
        0.038086        0.382300
        0.043457        0.435400
        0.045410        0.456100
        0.047607        0.477200
        0.047607        0.477200
        0.041260        0.414600
        0.031006        0.311000
>I have checeked my code.I doublt maybe something wrong with below:
>"sphere
        {
         <x1-center_x,y1-center_y,z1-center_z>,
         1.55
        pigment {color rgb spectral}
        }
"
>This is my code to define the objects in scene.I use sphere," pigment {color >rgb
spectral}" I doublt this statement i
s wrong,"spectral" is my reflection >value such as below which I saved them in txt,and
I tell pov to read. These >value
s are reflection ,and they are float values.However color rgb is  color >,maybe this
is wrong,I doublt,but I donot know
 ,beg a help! Greate gratitudes!
            0.220900
            0.375800
            0.375800
            0.346500
            0.277700
            0.355800
            0.396900
            0.441800
            0.442800
            0.382300
            0.435400
            0.456100
            0.477200
            0.477200
            0.414600
            0.311000
            0.189700

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