RE: Wood effect

["George L Smyth" <GLSmyth@xxxxxxx>]

> -----Original Message-----
> the Wood-effect was first reported in 1910 by a guy named Wood when
> shooting with a filter of 720nm. The effect is caused by the structure of
> the chlorophyll containing leafs, which absorb most radiation below
> infrared. Only green gets (mostly) emitted after beeing reflected in the
> parenchym layer of the leaf. Wavelengths above 680nm are reflected there
> with no absorbtion at all thus producing the nice light spots on the IR
> film.

Nope, chlorophyll has nothing to do with it, with the exception that it
allows infrared radiation to pass right through.  What happens is that
radiation gets bounced around within the spaces between the cells, and is
reflected back.  This is the same sort of thing that happens in newly fallen
snow.  It appears whiter because of the spaces between the flakes, which
allow light to bounce around and be reflected back more strongly than when
the flakes are close to one another.

george

---
Handmade Photographic Images
http://www2.ari.net/glsmyth/

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