Re: snow

[Claudio Mori <cmori@xxxxxxxx>]

>> can someone tell me what happens if I shoot the snow with an EIR film? I
>> mean: the white of the snow remains white or not?
>> Thanks for any help
>
>Claudio,
>
>Hmmmm ... interesting question. I guess it would depend on whether the snow
>reflects any incident infrared or not. I mean we would need to know the
>spectral reflectance of the snow and the spectral quality of the illumination
>that falls on it. Then we would be able to determine the spectral quality of
>the radiation reflected towards the camera lens. 
>
>Let us assume that snow reflects zero infrared. Then it is assumed that it
>reflects equal amounts of red, gree, and blue since we see it as white. 
>Now in
>the film all three layers are sensitive to blue, but this is filtered out by
>the yellow filter that you normally would place over the camera lens ... the
>#12 is it?. 
>
>Now the top layer is sensitive to blue and infrared and forms cyan dye where
>unexposed. The next layer is blue and green sensitive and forms yellow dye
>where unexposed ... so this layer essentially gets way overexposed and 
>being a
>reversal emulsion it produces no dye. The third layer is blue and red 
>sensitive
>and since there is lots of red light, that layer, which forms magenta dye, 
>also
>will have no dye in it because the red in the white overexposed the layer.
>
>So, the top layer, being unexposed due to lack of IR reflected from the white
>snow, will contain lots of cyan dye while the other two layers will 
>contain no
>dye and so the white snow will look cyan.
>
>The actual color will vary and will ultimately dependon the relative 
>amounts of
>R, G, IR exposures. Cyan-ish is probably right but I may be all wet on 
>this ...
>                                      
>cheerio,
>
>Andy  o o  0 0 o . o  Andrew Davidhazy, Imaging and Photo Tech
>       \/\/\/\/\/\/   http://www.rit.edu/~andpph  716-475-2592  
>________|        |____________________________________________

Thanks, I'll send any photographs after shooting in Austrian mountains 
next week. If it's welcome, obviously


_________________________

Claudio Mori
Vice Direttore ItaliaOggi
+39-2-58219259
Office  cmori@xxxxxxxx
Private c.mori@xxxxxxxxxxxxxx
        

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