Re: Auto-focusing and IR focus shift

[Jud Hofmann <hofmann@xxxxxxxxxxxxxxxxxxxxxxxxxxx>]

On 9/13/96, Dan Cardish wrote:
>When I used to use my old Minolta 9000 with IR film, I found that the camera
>had no problem focusing and giving me a valid meter reading with a B+W #92
>filter (similar, I believe to a Wratten 89B) on the lens, even though the
>filter is almost opaque (in sunlight I can just manage to see the outlines
>of some subjects, but too dark to focus by eye).

[snip]

>Has anyone else noticed the same with their autofocus cameras?


I use Canon EOS-1s.  I spoke with Chuck Westfall, the Canon rep on the
Compuserve photoforum about 6 months ago on this topic.  His reply was that
the system was focusing on the remnant of visible light - not IR, and thus
the focus would be in error.

Chuck is _very_ knowledgable when it comes to his Canon products, so I take
this as gospel as regards to the EOS-1.

Jud Hofmann


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End of INFRARED-PHOTOGRAPHY Digest 64
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