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[OM] Vivitar 90-180mm Aperture

Subject: [OM] Vivitar 90-180mm Aperture
From: usher99@xxxxxxx
Date: Sat, 25 Dec 2010 12:55:46 -0500
Macro Moose writes:

As you know, I recently was able to fondle one of these. It seems to me 
to be
too big and especially too heavy for
casual use by someone like me. I don't see myself using it without a 
tripod. I
think if I were interested in an MF macro
lens in that focal length range, I'd do what I've done before, carry 
the Tamron
90/2.5 , matched 2x tele-converter or,
less likely, matched extension tube:


I really appreciated and enjoyed that analysis but must quibble with it.

The matched 1:1 converter for the Viv S1 90mm is nice with a rotating 
tripod mount and optimized to keep the field flat
and reduce aberrations at higher mags. There is actually slightly less 
CA in the bokeh (Long CA?) with this combo at 1:1 then
the Cosina-Voigtlander 125/2.5 APO-Lanthar Macro---gasp--- but the 
later has a much brighter VF, better working distance and is more 
flexible going from infinity to 1:1 w/o fussing with a converter. One 
instantly loses 2 stops with the dedicated 1:1 adapter, has a very 
short working distance and the mag is limited to 1:2 down to 1:1---not 
always convenient. With a standard TC it is more complex but at 1:1 the 
working distance is the same
as the original 90mm--only really 180mm at infinity. It is no longer 
flat field (not a biggie in many (most?) situations) but aberrations 
can be
substantial if not stopped down.

I would bet money that the IQ at 1:2 at F5.6 with the VivS1 90-180 and 
working distance would be better than almost any 90mm on a TC.
I am not sure if the effective FL changes at 1:2 with this lens, but I 
don't think much. I think it should be farily easy to calculate
the Effective FL from the MFD at 1:2 using the thin lens formula, but 
will need another cup of coffee. Perhaps Moose or Dr.
Focus will do the heavy lifting.

That be said , the VivS1 90-180 macro is indeed too bulky and heavy to 
pack for many trips. The CV125 packs OK though it is heavy, because it 
is short.
For travel have taken the CV180/4 Apo close focus in OM mount (goes1:4) 
and bring an extension tube or two. It can fit in a coat pocket and is 
about as big as the lens hood for the longer FL F4 or F2.8 Canyon 
zooms. The bokeh can be a bit lively at times though.

Macro Mike
-- 
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