At 17:27 1/18/02, James asked:
I've been reading the debates about the 90/2 vs. the 100/2... and I've
been looking into the Auto Extension Tubes...
If I was to buy just one, which should it be for regular Macro work?
(Flowers, etc.)
The above is in direct reference to the 100/2.
Thanks, James.
James,
You didn't state how *big* the flower is. If it's of the full blossom of a
mature sunflower you won't need one! OK, that's a glib reply. Here's some
things to think about.
1. How much extension you need is based on magnification you want on
film. Size of the "flower" and how much of that flower you want on the
film will determine this.
2. How much extension you need is also based on focal length. To get 1:1
magnification you need to extend the lens an additional focal length from
its infinity focus position (100mm). Remember your lens can already extend
some to its minimum focus distance using its focusing ring. A typical
non-macro lens will extend about 1/6th to 1/8th of its focal length to
minimum focus distance (there are technical reasons for this related to
lens design).
Based on experience with doing macros using the 85/2 and 135/2.8:
1. Most used tube is 14mm.
2. Very closely following is the 25mm.
3. 7mm isn't used by itself very often with lenses of these lengths; it is
used more for stacking with the 25mm to get 32mm extension.
Alternative:
Find a Vivitar AT-21 set of 12mm, 20mm and 36mm tubes. These auto-tubes
are sturdy metal construction, much less expensive when found [typically as
a complete set], and their lengths are geared more for longer lenses than
the Zuiko tubes.
I have a complete set of both, and used the Vivitar AT-21 set with the 85/2
and 135/2.8 for some time while looking and waiting for good prices on the
Zuiko tubes. The Zuiko tubes enabled working more with the shorter lenses.
-- John
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