Re:do lens changes fog IR?

[Gary Beasley <beasleyglb@xxxxxxxxxxxxxx>]

>Date: Tue, 27 Apr 1999 02:14:15 EDT
>From: Llamapix@xxxxxxx
>Subject: do lens changes fog IR?
>
>I hope this is the right procedure to post a question...  Has anyone else
had 
>problems with fogging IR film when changing lenses?  I was shooting at
Joshua 
>Tree when a couple coyotes approached and I wanted a longer lens.  I changed 
>my lens without using a changing bag.  All my coyote pictures are flat and 
>have uneven exposure.  I can't quite tell if it's fog or not.  However, all 
>the other pictures on the roll have perfect exposure.  My friend says it's 
>because coyotes are tricksters.  I am looking for a more scientific 
>explanation.  The camera is an old Canon AT-1.  Thanks, Gregg
>*
>
If changing the lens fogged the film it's time to take the camera in for
repairs! What this sounds to me is likely a bad telephoto, either
condensation or fungus on an inside lens element. Hold the lens up to a
bright source of light with the aperture wide open and look through from
the edge. This usually shows more than most people want to see. A small
amount of trash usually don't hurt, but any trace of haze or fungus and the
lens is a doorstop.
Gary Beasley
http://beasleyglb.home.mindspring.com/

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