[Leica] Re: Aspherical lens 35 mm summilux

[cummer@asiaonline.net (Cummer Family)]

>
>From: "Frank Filippone" <red735i@worldnet.att.net>
>Date: Fri, 20 Feb 1998 07:37:48 -0800
>Subject: Re: [Leica] 35 f1.4 Aspherical/ASPH/Ein Stuck
>
>Bill... I need simplification....and a bit of help....
>
>The lenses on the Ein Stuck have 2 concave elements.  I have established
>that on 3 samples.
>
>I was not an LHSA member at the time of the VF article you noted.  I can
>not refer to any other characteristic of the lens than that I have noted to
>discriminate differences.  However, I assure you, the lenses noted use
>concave F+R elements.
>
>Everyone seems to want to say that these lenses were NOT the rare versions,
>but apparently there are only 2 versions of the 35 F1.4 aspheric lens...
>the
>Aspherical with 2 concave elements, and the ASPH with 1 concave element.
>
>Repeating the first sentence, above, my conclusion is that the Ein Stuick
>lenses, at least on the samples noted, using F+R concave optical elements,
>are the rarer Aspherical lenses.   
>
>Now the help......Are you saying there is a third version with concave F+R
>elements, but is an ASPH version? 
>How is that lens different from the other 2, noting we are talking about
>optical design and physical properties, and to a much different degree,
>although important, the markings on the lens?
>
>If you will be kind enough to answer, I will check the 2 samples I have
>access to.  Maybe we can definitively put this discussion to bed.
>
>Thank You
>Remove "ZZ" form auto reply address or 
>please reply to address below:
>
>Frank Filippone
>red735i@worldnet.att.net
>
>
Dear Frank,
I think you are confusing concave elements for aspheric elements on these
lenses. Page 148 of Dennis Laney's Leica Collector's Guide has a cross
section of the first version of the Summilux M 35 1.4 Aspherical. Both front
and rear elements are concave and the two aspherical elements are noted in
the diagram as being part of the *inside* second group and last group of
elements. I have from Leica Product Information circular VII/94/FAX/L
(August 1994) a diagram of the summilux M 35 1.4 ASPH - again there are
concave surfaces for the front and rear elements but the single aspherical
surface is located in a center element next to the aperture blades. Leica
differentiates between the first version and the second version as follows:
"The abbreviation "ASPH" added on to the name, applies to the aspherical
lens surface that provides this optical system with an unsurpassable image
performance. It is absolutely comparable to the Summilux M f1.4/35mm
ASPHERICAL of which a limited number was produced." (From the Info Circular
quoted above). If the lens says ASPH is has a single aspherical element. If
it says ASPHERICAL it is the first version with two aspherical elements. I
hope this is helpful
Best Regards
Howard Cummer