How does one install the #87 filter behind the lens and in front of the
shutter and can you still see through the lens or not;that is since the
#87 is opaque to visible light is this a possible way to use this filter
without having to remove it in order to use the viewfinder? I do not
understand why this results in correct infrared focus unless you are
just using the depth of field that you get with the aperture setting
that you are using.If this is the case then it would not matter where
the filter is placed as far as focus is concerned.It seems to me that
you are claiming that the #87 can refract infrared wavelengths to the
correct focus.I was not aware of this focus correcting ability of the
#87 filter.
-Gene Mayeda
Marco wrote:
>
> On Mar, 3 feb 1998 14:26, Thomas H. Hogan <mailto:flzhgn@xxxxxxxxxxxxx>
> wrote:
> >Although it does not have an Infrared Focus Mark my pictures
> >turn out with correct focus using an opaque IR filter (#87) behind
> >the lens but in front of the shutter in an OM1n.
> >
>
> Nor have the other 35-70. In a test made by an Italian magazine, I found
> the f/4 to be *very* corrected as chromatic aberration. Blue-green light
> (500 nm) meets exactly the red (650 nm) value (at 50mm of focal lenght).
>
> Marco
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