PJ writes:
In response to my comment on the 50mm f/3.5:
> >While you could then use the tubes with the f/3.5, they
> >required that the lens helical be racked all the way out to kick in close
> >focus aberration correction.
P.J. asked:
> You lost me there. I suppose Gary will send me an explanation, but I
posted
> here since others might have been confused by that one.
There are floating elements in a few of the Zuiko lenses, including the 50mm
f/3.5 They move as one focuses closer and closer, in order to correct for
aberrations. Putting an extension tube on one of these floating element
lenses might lead to you changing the focus (turning the helical) to fill the
frame the way you want. Theoretically, you are then defeating the
corrections made by the floating elements. In another words, you might be
setting the lens to 10 feet or 20 feet, or even infinity - depending on how
much you changed the focus on the helical. To use the tubes correctly, you
first focus the lens as close as it can get and then put a tube on. You are
limited to the magnification rations you get when the tube(s) is in place.
This "stepped" limitation in magnification is rather a pain in the behind.
That is a major limitation of macros that incorporate floating elements.
(The second is that they decrease in focal length the closer you focus!)
Plus the 50 and 90mm macros aren't even optimized for greater than 1:2
magnification.
P.J. wrote:
> I'm new to macro work but am fortunate enough to have the 50mm 3.5 (I made
a
> visit to the camera store in a weak moment.) Anyway, I want to expand my
> distance to subject. I know one solution is to go with a larger focal
> length. Is that my only option? How will extension tubes change my image
> ratio and my distance to subject?
Extension tubes increase subject magnification and require you to get
progressively closer. If you want to back off, try the 135mm f/4.5 Macro.
I wrote:
> >Warning: you will eventually be eyeing the 80mm 1:1 and Telescoping Auto
> >Tube.
PJ responded:
> Is this a reference to the 80mm which works with the auto bellows and is
> manual or another macro lens I don't know about? And if it is, then how
> much
> of a pain is the auto vs. manual lens and extension tubes, for that
matter,
> when composing and taking a photograph.
The 80mm and 135mm lenses work as automatic aperture lenses with the
telescoping extension tube, combinations which aren't a pain at all! For the
best quality from 1:2 down to 1:1, use the 80mm plus telescoping extension
tube. The close up lens for the 80mm allows you to go to 2:1
Final note: Forget all of this and just shoot whatever you have and see if
you like the results. If you do, then you have saved yourself a ton on money
that can go elsewhere. Doing macro work the way perfectionist Olympus
designers developed the system is EXPENSIVE. But, they addressed the
problems in designing lenses for greater than 1:2 magnification and many
other manufacturers just made their macros go to 1:1, regardless of inherent
optical limitations. In another words, marketing dictated that engineering do
it, whether or not it was feasible from a performance point of view. Within
Olympus, they just said "no." That's laudable.
Gary Reese
Las Vegas, NV
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