[rollei_list] Re: OT: Leica vs. Zeiss
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <rollei_list@xxxxxxxxxxxxx>
- Date: Wed, 18 Nov 2009 07:40:17 -0800
----- Original Message -----
From: "Frank Dernie" <Frank.Dernie@xxxxxxxxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Tuesday, November 17, 2009 9:54 PM
Subject: [rollei_list] Re: OT: Leica vs. Zeiss
Actually Apo is a typo in the case of this lens as such an
item does not exist. The latest 50mm f1.4 is Aspherical not
apo. It is by a long way the best f1.4 lens I have used wide
open, and I have used a few. The new-Zeiss 50 f1.5 sonnar is
reported to be a retro lens and is soft and suitable for
portraits wide open, though I have not used one personally.
Only 2 Leica M lenses are marked Apo, the latest 90mm f2 and
135mm f3.4. I would be prepared to bet five bob that they
really are apo...
The Leica lenses I have, which is quite a few, may not all
be apo, whether marked thus or not, but they show noticeably
less chromatic fringing than most of the fast lenses I have
from Nikon or Canon. FWIW.
Frank
Well, aspherical is something else again. Actually, of
course a lens can be both. Aspherical surfaces have been
known for a very long time but its been only recently that
they could be more or less mass produced to make the costs
reasonable. In the past aspherical surfaces had to be hand
figured.
Its possible to duplicate an asphere with spherical
surfaces, in fact that is how lenses are made, however, a
single aspherical surface can take the place of several
combined spherical surfaces for the same amount of
correction.
The Zeiss Index shows several experimental lenses with
aspherical surfaces dating back to the 'teens. The Zeiss
index was a compilation of notes on lenses generated
internally by Zeiss, I think mainly Willie Merte. It is
interesting because it shows lenses never offered
commercially and internal analysis of competitor's lenses. I
have it as part of the lens survey program LensView.
If Leitz publishes chromatic aberration plots of the
lenses it will be easy enough to tell what sort of
correction they have. An achromat will have a parabolic
curve going through the center line twice, an apochromat
will have an S shaped curve going through the center line
three times. Rodenstock has plots for several of their
lenses, the ones called APO are clearly achromats.
--
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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