The Telescopic Auto Tube 65-116 will mount any Oly lens, but is only
actually suited for a limited number. The name describes it, it is a
variable length extension tube with minimum extension of 65mm and max of
116 mm. It is specifically designed to work with the series of Zuiko
true macro lenses of 135, 80, 38 and 20mm to continuously cover from
infinity to 12x (i.e. the image on film is 12 times the size of the subject.
The 50/3.5 macro lens focuses from infinity to 0.5x. Oly says "
Combined with Extension Tube 25, the reproduction ratio is extended from
1/2 to 1:1 life size. However, to obtain best results in this range, the
use of the 1:1 Macro 80mm/F4 (with Auto Bellows) is recommended. Use
with 65mm or more of extension would give higher magnification, but with
poorer performance, as the lens would be considerably outside the
magnification for which it was designed.
The range of 65-116mm is theoretically much more useful for longer
lenses, like 135mm and longer, where it's length is a smaller proportion
of the focal length. However, the tube isn't mechanically designed to
carry heavy lenses, so care and/or special support arrangements are
necessary. I believe a listee has reported using it with a 200mm lens
with good results.
A word about macro. To manufacturers of true macro equipment, macro
means the ability to produce a sharp image with a flat field (flatter
than a conventional lens) in the design range of magnification. Thus
when I copy flat images onto slides for University lectures, I use true
macros, the Zuiko 50/3.5 and the Tamron SP 90/2.5. However, for many
photographers, macro mostly means images of small 3-D objects which will
only be in focus in the central part of the image anyway for DOF
reasons. In this case, less rigorous rules apply, and good results may
be obtained with many conventional lenses in combination with extension
tubes and close-up lenses. Another trick when using a regular 50mm lens
to go closer than 1/2x or so or a 50mm macro beyond about 1x, is to use
a reversing ring so that the reversed subject and object distances are
closer to the range for which the lens was designed. Some zoom lenses do
a good job with this kind of macro work at ranges down to about 0.75x.
Examples are the Tamron SP 60-300mm and the Tokina AT-X 50-250mm.
Ther is also a lot of great info in the Oly Macrophotgraphy Manual.
<http://olympus.dementia.org/eSIF/om-sif/macrophotogroup/manuals/macrophotogroup.pdf>
Although more awkward to use in the field, the Auto Bellows is much
better suited to use with a 50mm lens because of both its shorter
minimum extention and its ability to reverse the lens without another
adapter. Normal and reversed magnifications and subject distances with
the 50/3.5 and the bellows are here
<http://olympus.dementia.org/eSIF/om-sif/macrophotogroup/auto_bellows.htm>.
Moose
Andy wrote:
Hi all -- I'm new to this list and to the Olympus OM system. I'm
interested in nature photography and macro work and have a question
about the telescopic extension tube. Olympus literature states it is
to be used with only a few specific macro lenses (like the 135mm and
85mm). I have heard that it works with other lenses as well. Is this
true, and if so, is it a useful tool with the other lenses (including
for example the 50mm macro)? Thanks in advance. Regards, Andy Rothman.
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