From: "Clemente Colayco" <litefoot@xxxxxxxxxxxxxxx>
On what oly lenses will this work effectively?
Lens manufacturers tend to zealously guard their lens formulas; so it's hard
for a competitor or third party supplier (e.g., Vivitar) to match formulae
specs unless they are provided by the manufacturer. This appeared to be the
case with the matched multiplier TCs for major manufacturers that Vivitar
offered back in the '70's. However, Zuiko lens formulae has changed with
the new space age optics (roughly speaking, those lenses produced circa
1980+---20/2 MC, 21/2, 24/2, 24/3.5 PC, 28/2, 38/2.8 MC, 50/1.2, 50/2 MC,
90/2 MC, 100/2, 135/4.5 MC, 180/2, 250/2, 350/2.8, & 35-80/2.8) and I am
unaware of any third party company who knows the formulae of these recent
offerings.
Since the TC degrades resolution and contrast, it should only be employed to
get yourself out of trouble. In a pinch, I use my Vivitar 2X macro TC with
the 90/2 (to produce a 180/4 MC with 1:1 M---note that the TC does not
affect minimum focus) and with the 180/2 (to produce a 360/4 super tele). I
would not hesitate to use it with the 50/1.8 if I left the 90/2 behind.
Eventually, I would like to add a 250/2 or a 350/2.8 (or both!) as my super
tele-ware.
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