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[OM] CU and teleconverter notes

Subject: [OM] CU and teleconverter notes
From: Wayne Shumaker <om3ti@xxxxxxxx>
Date: Tue, 20 Jul 2021 07:28:52 -0700
I was looking into getting a 1.4x teleconverter for closeup magnification and 
came across these photons to photos articles from 2007.




The interesting point for me was that the teleconverter not only changes the 
focal length, it also moves the rear node. He states:

"In a surprising twist, the effect of the TC multiplier decreases as the 
magnification of the primary lens increases and can go below 1 resulting in a 
decrease of focal length as you focus closer."


"Although focal length may not be as expected at closest focus, magnification 
is increased as expected; and a TC can be a surprisingly good way to get more 
magnification for close-ups."

He does not mention working distance, so I expect, if his example is true that 
although increased magnification, the focal length could be less at close focus 
with the teleconverter, which I am assuming might also decrease working 
distance. Working distance with teleconverter at the same magnification, I am 
assuming, does increase working distance? hmmm??

I guess the empirical approach is best, except when money is involved.

Optically challenged - WayneS

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