Re: Infrared dilemma

[boblong@xxxxxxxxxxx (Robert Long)]

On Sun, 10 Nov 1996 20:14:59 +0000 (GMT), you wrote:

|I've run into a situation that I don't understand.  Using Konica IR =
rated at
|ISO 32, with a #25 red filter, and a polarizing filter, all of my shots =
came
|out great.  Now, while using a 20mm lense, the frame corners are all =
clipped,
|resulting in a round exposure. This only happens with IR film.  Could it=
 be
|that the extra filter at the front of the lense be the problem? =20

Absolutely!  With any responsibly designed wide-angle lens, a single
filter or whatever of the appropriate size for the front thread should
cause no vignetting.  But add a second one and you're on your own.
And polarizers generally are thicker than filters, compounding the
problem.

The solution is to use a step-up adapter either between the filters or
between the lens and the filter pack.

Bob Long
(boblong@xxxxxxxxxxx)

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Topic No. 4