Archived posting to the Leica Users Group, 2001/03/19

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Subject: Re: [Leica] 12mm Heliar UW
From: TTAbrahams@aol.com
Date: Tue, 20 Mar 2001 00:48:57 EST

Mike, I would be careful with the rear mounted filter on the 12/5,6. Unless 
you make the tube shallow enough to have the filter literally touching the 
rear element, you might induce vignetting. The 'rays" coming out of the rear 
of a 12 are coming out in a steep angle, at least the corner ones. I would 
try it, of course, but I would not be surprised if you get degradation in the 
extreme corners. A better solution would be to get the 77mm filterholder from 
Voigtlander and go and talk to your local Movie Supply House. They can 
provide either Roscoe or other makes of filters in just about any spectral 
sensitivity. All you have to do is to cut the gel to an appropriate size and 
stick it in the 77mm filterholder. You could even cut a small slot in the gel 
to match the "see-through" slot in the filterholder.If you could find a 
defunct 77 filter and remove the glass, you could use the filter-ring as a 
template for cutting the filtergel and to hold the gel in place in the 
holder.  I have a fetish for not using any filters at the back of a lens, 
unless the lens is designed for it. Rear elements are critical, any damage 
there shows up as a very distinctive mark on the neg.
 In any case, it could be an interesting image with the 12/5,6 and IR film. 
Talk about wide-open spaces glowing and the black sky! If it works, please 
post some images.
Good luck,
Tom A

Replies: Reply from Henning Wulff <henningw@archiphoto.com> (Re: [Leica] 12mm Heliar UW)