I was looking into getting a 1.4x teleconverter for closeup magnification and
came across these photons to photos articles from 2007.
https://photonstophotos.net/GeneralTopics/Close-up/How_TeleConverters_Affect_Magnification.htm
https://photonstophotos.net/GeneralTopics/Close-up/How_Close-up_Lenses_Affect_Magnification.htm
https://photonstophotos.net/GeneralTopics/Close-up/How_Extension_Tubes_Affect_Magnification.htm
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."
and
"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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