Near IR Visual Observations

This was a serendipitous discovery made using an unexposed black Fuji
Sensia slide film tail I was about to throw away.

It is well known that the dye based films do not block IR and so are
dangerous when used to make the suns visible light intensity bearable.
The piece I had was sufficient to cover both eyes and seal well enough
to gain a reasonable level of dark adaptation in full daylght.

Initially the image was monochrome and faint, but after about 30s of
dark adaption the image came back into full colour. Grass and foliage
was no longer green but light and red or orange coloured. The sky
became a deeper blue. The effect is most striking when the sun is
behind you and there is strong contrasty sunlight.

It seems that the eye has some residual sensitivity to the
unattenuated near IR when the bulk of the visible light has been
filtered out. The visual oberservation of these "false" colour views
is quite interesting. I have tried it with a couple of other people
and they also report seeing red grass and orange trees after adjusting
to the dimness.

I expect it will work similarly with most other dye based colour slide
films. Perhaps with some colour bias.

Regards,
Martin Brown

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