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Re: [OM] 7mm Macro Extension Tube

Subject: Re: [OM] 7mm Macro Extension Tube
From: "Paul Farrar" <farrar@xxxxxxxxxxxx>
Date: Thu, 27 Aug 1998 09:21:06 -0500 (CDT)
> 
> Hi Bob:
> 
> > When would something like this be useful?  How much effect will it have
> >  and which lenses would be best suited to its use?
> 
> The shorter the focal length, the more effective this is in being able to
> focus closer.  For example:
> 
> 35 mm f/2.0 Zuiko
> 1:5.3 reproduction ratio normally
> 1:4.3 w/ 7 mm tube
> 
> 28 mm f/2.8 Zuiko
> 1:6.3 normally
> 1:2.3 w/ 7 mm tube
> 
> 24 mm f/2.8 Zuiko
> 1:6 normally
> 1:2 w/ 7 mm tube
> 
> But frankly, I can't remember having the desire to focus my wide angles closer
> than normal, so mine is still looking for a reason for its existance.  Given
> that it weighs close to that of the 25 mm tube, I'll opt to carry the latter,
> which gets the 50 mm Macros to 1:1 (in a pinch) and offers a bit closer
> focusing with telephoto lenses.
> 
> Gary Reese
> Las Vegas, NV

I've used it mainly on the 180/2.8. It changes the range from 2m-inf
to 1.5-5m, which is more useful with people. Except for the 180/2, 250,
and 350, OM telephotos are older unit focusing designs that are a bit
long on the nearest focusing range, so short tubes are needed for many
uses.

With close focusing correction lenses like the 50/3.5, you should always
use the shortest tube possible, so the 7mm is needed if you go just
beyond 1/2x.

Paul Farrar

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