Re: Fw: IR 750 Sensitivity

[ADavidhazy <ANDPPH@xxxxxxxxxxxxxxxxxx>]

Chris,

> OK, so to clarify so that I understand the answer you gave, does all light
> contain some IR?  Even fluorescents?  Thus if an object is lit by any source
> there will always be IR there?  Then I'll lay this thread to rest.

No. But first off let's lay the "expert" stuff aside. I just try like anyone
else to understand life and the forces that shape it. !!!

Anyway, not all light contains IR. So when the suggestion was made to combine a
green filter with a fluorescent tube and using it as a safelight for processing
film that is presumably sensitve to blue, red and infrared but not to green, I
agreed that that was a practical thing to do. (assuming the kind of fluorescent
tube we are dealing with does not emit IR ... 'cause some might)

If the light had been a tungsten lamp, however, then one would have had to use
an IR blocking filter in addition to the green filter. 

Of course the assumption is that the green filter transmits little is any blue
or red (by definition that is true but in practice it may not be)

A green LED presumably would only emit green and thus be useable solo.

In any case, in any situation where one is trying to predict the outcome it
pays to know something precise about the spectral qualities of the sources, the
filters and the receptors ... and sometimes even of the "medium" (air
generally) itself. 

>      And, BTW, I love a manhattan (emphasis on "a").  Maker's Mark.  Sweet,
> tho. None of that olive stuff.

The "a" leads to "another" ...

andy
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