Archived posting to the Leica Users Group, 2001/11/29

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Subject: Re: [Leica] Re: DR-SUMMICRON - with strange aperture scale
From: Eric Calderwood <eric.calderwood@btinternet.com>
Date: Thu, 29 Nov 2001 13:26:39 +0000

Seth

I have just unscrewed the lens head on my DR Summicron an do indeed see the
inscription you mention.
My lens number 1833907 is marked 51.9 N , hope this is info is of some help.

Best Regards
Eric

(Liverpool U.K.)

> Dan:
> 
> I wish I knew. I've not seen that before. I will make a guess but remember it
> is pure guess: the 39 was on the lens at birth, meaning 53.9 (although I
> don't recall ever seeing a number that high). Then the lens was rebuilt,
> perhaps in order to be a dual range, and became 51.9 N(ew)? Just conjecture.
> Can't figure out what else it might be. The fact that the second set of
> numbers is of a differrent size makes me wary that it may not have been the
> factory that did it.
> 
> I also wonder if you have noticed any problems with focus? If the lens head
> is misfitted, your photographs should be somewhat out-of-focus.
> 
> John Collier is correct though: you need to have the lens examined by a
> really competent repair facility that knows what it is doing to regularize
> whatever is going on with your lens. Incidentally, what is the serial number?
> 
> There were two changes in the DR/Rigid Summicrons: the coating was changed on
> the later lenses and improved to enhance contrast. And the focussing mount
> was also changed. The first series has the grooves that are cut into the
> focussing ring on the outer raised surfaces of the ring; with the later
> lenses, the grooves are cut into the indented scallops of the ring. I'm not
> sure that the changes took place simultaneously not what were the serial
> numbers at which changes occurred.
> There has always been some conjecture that the optical formula of the lenases
> was also changed. I have correspondence with both Wetzlar and Solms that
> confirms that the actual optical design - apart from the coating modification
> - didn't change throughout the production run, 1956-1970.
> 
> Because your result with the numbers and this response might be interesting
> to LUG readers, this technologically challenged LUGGER is going to try to
> forward both.
> 
> Best,  Seth           LaK 9
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