Archived posting to the Leica Users Group, 2000/11/27
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on 27/11/00 10:22 AM, Mark Rabiner at mark@rabiner.cncoffice.com wrote:
> I find it interesting (for my Protracted argument) that Leica went with front
> close up glass instead of rear tubes like all the other companies did as the
> attachment to bring their 100 2.8 apo macro from 1:2 to 1:1!
Hi Mark,
I understand that the 100 APO design is somewhat akin to a zoom in its
optical structure and that like zooms it does not work well with extension
tubes: zooms (and the 100 APO) only focus with one group of elements rather
than the usual shifting of the whole lot back and forth as with other
lenses. You tend to get uneven sharpness and excessive curvature of field
with tubes or bellows behind a zoom and so too with the 100 APO, so I am
told. The same thing happens with IF fixed lenses IME (really blurry away
from the centre of the image), which is probably why many of the AF systems
do not offer extension tubes or bellows to the extent that was common with
the good old MF systems.
I have used the Canon 500D 77mm (2 or 3 elements?) close-up lens with
excellent results on my 70-200 Canon and recently with the Leica 70-180: a
huge contraption that gets really close and you can focus by zooming (weird
heh?). It also terrifies living things (except children who just want to
touch the pretty glass) long enough to freeze them to the spot whilst you
photograph them.
Rs
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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