Archived posting to the Leica Users Group, 2000/11/28
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on 29/11/00 4:46 AM, imx at imxputs@knoware.nl wrote:
> Adrian wrote in part about the Curvature of Field when taking macro pictures
> with the Apo 100 and using bellows or extenson tubes.
> Here are the facts: The APO 100 is NOT a zoomlens design. It is a standard
> Double Gauss with a two element rear group to improve macro capabilities.
> The story that zoomlenses and internal focusing lenses are not as good when
> using tubes than lenses where the complete optical cell moves when focusing
> is not true.
Oh dear Erwin - I seem to have erred! Well perhaps you can give us the low
down on why Leica chose to use the Elpro approach for 1:1.1 to 1:2 for the
100 APO.
I did not say the APO 100 is a zoomlens design, rather that it is 'somewhat
akin to a zoom' in that it has a focussing group of elements and another
set, [which in this case are stationary]. I have a vague recollection of an
interview with Lothar Kölsch in which he mentions zoom lens design as
playing a part in the optical construction of this lens (his first for
Leica?). I understand that one of the main advantages of the Elpro vs tubes
on the 100APO is that it keeps the field very much flatter. Also why does
Leica consistently recommend not using extension tubes with zoom lenses?
'The story' as you put it was 'IME' and I stand by it: I do not get as good
results with IF and zoom lenses on tubes as I do with lenses where the whole
optical cell moves. With the 70-180 and the Canon 70-200 for example I get
much better results using the Canon 500D closeup lens than tubes and
likewise the 90 Summicron is quite usable on extension tubes whilst the
Canon 100/2, an IF lens, is not: both are excellent lenses in regular
shooting. None of the dozen or so zooms I have tried to use on extension
tubes has offered usable results: far too much curvature of field. My
experience is however limited to a handful of lenses and practical photo
taking in the field and no theoretical exercises nor rigorous investigation:
for that I read and respect your reviews. I look forward to your forthcoming
book.
In the meantime I wonder if you can help: my 90/2 R lens is a recent
secondhand purchase and I am surprised to find it has a quite different
colour balance to all my other Leica lenses. It is distinctly warmer in
rendition, even more so than the Noctiluxes which I have owned (1 and 1.2
which are the only recent Leica lenses to have been acknowledged to have a
non standard colour bias - to the warm side). I would say the shift is
similar to an 81a filter and is discernible in photos and even to the naked
eye looking through the lens. Can you explain how this came about - I am
told by Solms that it is not normal? In the meantime I find I rather like
it: it enhances the portraits I take with it and for which I bought it. Of
course with BW it is not an issue. I am not in any hurry to get it fixed but
wondered what might have caused this shift in colour balance if indeed it
has shifted from how it left the factory.
Bests
Adrian
- --
Adrian Bradshaw
Corporate and Editorial Photography
Beijing, China
tel/fax +86 10 6532 5112
mobile +86 139 108 22292
e-mail apbbeijing@yahoo.com
OR adrianpeterbradshaw@compuserve.com
website: http://www.apbphoto.com
http://www.liaisonintl.com/bradshaw.htm
http://www.liaisonintl.com/bradshaw_e.htm
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