Re: Photographing flowers

[NFOTO Bjorn Rorslett <nikon@xxxxxxx>]

At 10:05 05.05.97 +0300, you wrote:
>Hello!
>
>I have questions about photographing flowers in the spring time,
>especially taking photos of blue flowers.
>
>Almost every time I have photographed blue flowers they come out
>with some sort of red or magenta cast. Light blue turns to pink and 
>deeper blue turns to magenta or red.
>
>I have seen various explanations for this in photographig magazines.
>Some say that it has something to do with flowers different reflectance
>to the infrared light, and some say it is the ultraviolet light.
>
>Now I would like to know what is the explanation for this phenomenon?
>
>The color shift happens with both color negative and slide film when
>photographing blue flowers. Why only blue?
>Could this be avoided with some special filtering?
>
>If this is connected to the infrared light, then maybe there are
>strong effects to be seen when using IR film?
>
>How sensitive to the IR and UV light are the normal
>colour negative and slide films?
>
>Maybe I have now too many questions, but  I hope there are some
>experts in this list who could give some answers
>
>
>Hannu Jarventaus
>Espoo, Finland

Your problem is caused by several factors. First, the petals of the flowers
reflect IR quite strongly. Second, many (most modern) colour films have dyes
with a red sensitivity extending into the (very) near IR. Fuji Velvia is a
typical example. It is sensitive to far red up to at least 720 nm. The
petals reflects strongly here and this imparts a reddish tinge to the blue
flowers. A very pale blue filter usually brings the colours right, and
shooting in open shadow or under overcast conditions may help too.  

Rest assured that UV is not the culprit causing your flowers to turn red.
Nearly all colour films have an efficient UV-screening layer so as to make
them very insensitive to UV. If they were to render UV onto the film, that
would have given the flowers a bluish cast which isn't what you observed. By
the way, modern film's low UV sensitivity is the chief obstacle to doing UV
colour photography. 

regards/bjorn

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


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