RE: Infrared & Water

[Rolland Elliott <liquidriver@xxxxxxxxx>]

Here are the specific IR trasmission numbers from the
graph on page 168 of "Photography by Infrared, Its
principles and applications" This is through 1 cm of
water. The numbers are rather close together on the
graph, but they are reliable plus or minus 1
percentage point.

900nm  90% Tranmission
850nm  95%
800nm  99%
750nm  98%
700nm  98%
650nm  98%
600nm  100%

When I get time I will scan it and post it to the web.
As one can see using a 25 Red filter will allow rather
good penetration. It's not until you use an opaque
filter like the 87C with a 50% tranmission point of
about 830nm that you will start getting into the lower
95 to 90% transmision zones.

Peace Rolland 





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