Archived posting to the Leica Users Group, 2000/06/11

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Subject: [Leica] Rear element spots
From: "Julian Koplen" <jkoplen@mindspring.com>
Date: Sun, 11 Jun 2000 12:58:01 -0400

I noticed that my 180mm f/3.4 Apo-Telyt-R was calling for about 1/2-1 stop
more exposure than I was expecting under "sunny 16" conditions.  In
comparison with the 50mm Summicron on the same camera (R8), the 180 was
indeed calling for about 1/2 stop more exposure.

In daylight the 180 glass looks perfectly clear and unclouded, but when I
peer through the lens front-to-rear against a darkened background and shine
a flashlight across the rear element, then the rear element seems to light
up with numerous tiny bright specks, like many stars against a night sky. (I
haven't had the nerve to subject my other lenses to the same test.)  There
is no gross deterioration on picture quality, but I'm not confident I could
tell if there was just a modest decrease.

I'm sure I'm going to feel compelled to send the lens to Sherry for her
inspection, but can any of you LUGGERs give me an opinion based on your own
experience? I briefly entertained the notion that the difference in exposure
readings was due to  more elements in a telephoto, but I believe that was
just wishful thinking.

Thanks for any help..........Julian

Replies: Reply from Rick Dykstra <rdandcb@cybermac.com.au> (Re: [Leica] Rear element spots)