James writes:
> I want to photograph objects about 1-3 mm in size and have been told that a
> 20 mm macro is the lens of choice.
With the Auto Bellows you can get up to 16X magnification. That isn't good
enough for objects 1 mm to about 1.9 mm wide, though You need a microscope
for those, or shoot them at less than full frame and enlarge more (a good
microphotographic technique for getting better depth of field).
> I assume the f2 (vs. f3.5) is the
> correct lens.
Yup, for the auto diaphram model it is. The older 20mm f/3.5 preset will
also work, but wide open it already shows the effects of diffraction at f/3.5
!! Since you can't stop down much at all at these magnifications - with a
limiting aperture of f/2 for 14x and 16x and f/2.8 for 12x and 10x - the auto
diaphram isn't much needed.
> Any suggestion where such a lens (used) can be
> obtained in the USA?
>From anyone who stocks Olympus equipment. Just special order it.
Gary Reese
Las Vegas, NV
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