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[OM] Re: 180/2 for macro?!

Subject: [OM] Re: 180/2 for macro?!
From: Moose <olymoose@xxxxxxxxxxxxxxx>
Date: Mon, 26 Jul 2004 22:55:05 -0700
Reading your posts on combos, that's what I was wondering about. Oly's 
teleconverter designs seem to be very focused (tee hee) on getting the 
front element of the converter as close as possible to the rear element 
of the prime lens. The result is that the 1.4x will only physically fit 
a few lenses and the 2x won't fit some lenses it would seem logical for. 
For example, I would like to use the 2x with the 90/2 to make a 180/4 
macro lens, but there is not enough clearance for them to match. This is 
something I used to do with the Tamron SP 90/2.5 and their 2x.

I have always assumed that Oly would only have made these design 
decisions which limit the potential uses of their teleconverters (and 
presumably limit sales) if there were a performance advantage. The 
reports of some list members that the Oly 1.4x outperforms the Tamron 
1.4x on Tamron tele lenses might bear this out. It seems to me that the 
angle at which the light enters the converter would have a significant 
effect on design and performance. With 2 25mm tubes in front of a 
teleconverter, with the lens set at infinity, it would actually be 
receiving the light after it had come into focus at the expected film 
plane 46mm behind the mount, so it would be diverging, rather than 
converging, when it hit the converter.

Moose

W Shumaker wrote:

>One thing I have not considered though is how optimized the
>1.4x teleconverter is to the lens design. That is, does it only function
>well when it is directly attached to the lens rather than pulled back
>from the lens via extension. I have a simple understanding of
>teleconverters.
>



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