Re: blue flowers

[NFOTO Bjorn Rorslett <nikon@xxxxxxx>]

At 18:35 05.05.97 +0000, you wrote:
>On  5 May 97 at 8:16, Geoff McAuliffe wrote:
>
>> Hannu Jarventaus was concerned because slides or prints of blue flowers 
>> did not accurately represent the blue of the flower:
>> 
>> I have had this problem using Ektachrome Elite to photograph blue Iris, 
>> the color is "off". I don't think it is an infrared or ultraviolet 
>> problem. I think this is due to a "conflict" between the pigments in the 
>> flowers and the way a particular slide film records these colors. Since 
>> different slide films are known to give slightly different 
>> representations of the same color, the "solution" is to try a 
>> different film. Color correcting filters might also be of use. 
>
>You might want to do check the sci.optics newsgroup archives 
>(altavista & dejanews) on the difference between violet and purple.
>Violet is a pure color, purple a mixture of blue and red, for which
>our eye has a different 'taste' than violet. This might explain the
>difference between visible impression of the real subject and its
>image on film. Has something to do with overlapping color ranges in
>the eye as well as those on film. I believe this overlap is also what 
>makes it almost impossible to estimate color effects on Ektachrome 
>IR.
>

>
>Willem-Jan Markerink
>

WJ is correct in pointing out the difference between violet and purple. I
take the opportunity to elaborate a little more on my first answer to Hannu
Jarventaus, because this ties in with WJ's remarks.

Because our eyes react to the difference between violet and purple, the
reddish cast to blue flowers, caused by near-IR reflectance and extended red
sensitivity of films is immediately apparent. Careful test shooting will
reveal that some films, for example Fuji Velvia, also will record purely red
flowers with too high red saturation in sunshine. This film gives under the
same conditions a reddish tinge to yellow to make true yellow flowers
orange. So, the effect caused by its far-red (up to 720 nm) sensitivity is
not confined to the rendition of blue flowers.

regards/bjorn

visit my UV Colour site at http://hawk.foto.no/pinhole/nikon/index.html 

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