Archived posting to the Leica Users Group, 1997/02/18

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Subject: Re: Pinhole aperture info
From: photology@juno.com (Thomas P Myro)
Date: Tue, 18 Feb 1997 22:31:55 EST

On Wed, 19 Feb 1997 00:41:19 +0800 Soon Wai Hoe <adisoon@pl.jaring.my>
writes:
>I tried piercing a hole in a Leica bodycap but the diameter of the 
>image
>circle was only the breath of the negative. What should I do??
>
>--Adi 
>
The reason your pierced hole in the bodycap failed as a true pinhole, is
because the
cap has substantial thickness to it.

Drill a large hole--8mm should do it, in your body cap, and mount a peice
of heavy metal foil-- brass shimstock will work just fine-- heavy
aluminum if you must. with a pinhole DRILLED in it (less than 1mm for
50mm's of extension).  This should solve your vignetting problem.

The explanation of this is that the angle of aperture, in this case, is
formed at the front of the hole, and is vignetted by the back of the hole
in thick materials.  There should never be a coverage problem with a
pinhole aperture.  The original camera-obscuras covered large walls with
a small aperture.

Sincerely,
Thomas P. Myro
Photology@juno.com