Re: Stigmata

["Karl & Anita Shah-Jenner" <shahjen@xxxxxxxxxx>]

Peter writes:<clip>
>So I guess in an effort to dispel the ongoing myth of what IR film can do,
>the short answer to your question is , no unfortunately it won't pick up
>warm blood.

>Can anyone explain from a scientific point of view why the veins are darker
>on IR film and not standard B&W film?  Is it because the skin is
>translucent to IR and so the dark vein structures are picked up better?

Hi all, (Hi Andy and anyone else who knows me ;-)

first, I'm new to the list so thanks all in advance for putting up with me!

I would suggest the reason blood looks darker under skin is that :
a) human skin is designed to reflect heat, hence it appears pale. (but
you're right, it is translucent, so some light does penetrate and diffuse)
b) human skin and the sub-dermal layers are largely composed of fats, long
chain proteins, reflective to IR - and not very much water.
c) blood IS composed largely of water and as anyone who has taken a photo
across a body of water will attest, water absorbs the wavelengths of IR that
IR film records and thus looks dark!

Conventional B&W films work in the visible spectrum and as we know - skin
tone as we perceive it is much the same as film will interpret it
(tone-wise).. .if veins are visible to us, they will probably be visible to
the B&W film too.  We're just surprised with IR renderings as sometimes the
IR film sees veins that we don't.

simple! :-)

Karl
West Australia

*
****
*******
******************************************************
*  To remove yourself from this list, send:          *
*         UNSUBSCRIBE INFRARED                       *
*       to                                           *
*         MAJORDOMO@xxxxx                            *
*----------------------------------------------------*
*   For the IR-FAQ, IR-Gallery and heaps of links:   *
*  http://www.a1.nl/phomepag/markerink/mainpage.htm  *
******************************************************