Hi all,
Thanks for your replies regarding the question about the bellows usage!
A few short comments:
[Chris:]
This is perfectly true, the moveable element gradually shifts as the
focus is moved to its minimum distance (1:2 magnification). Copying
slides clearly need at least 1:1 so I would expect to use the lens at
its maximum extent rather than extend using the bellows.
Yes, this does make sense. So I would expect to have to set the lens to
infinity whenever using higher magnifications that 0.5x lifesize (i.e.
whenever I put the lens on the bellows or ext. tubes or pushing it beyond
the built in 25mm of extension).
The Bellows manual confuses things further by stating that the lens
should be at infinity when used in the normal position and at closest
focus when used reversed.
This is a thing which indeed obfuscated things a bit... Either way, I expect
this to be correct, so from now on whenever I mount the lens on the bellows
I will just use it at infinity when not reversed, and when it is reversed, I
will set it to the closest focussing distance.
My experience of slide copying with the bellows and 50mm macro is that it
is difficult to extend the lens when using the bellows and slide copier
together as the bellows doesn't collapse to a small enough length to give
1:1.
I tried it quickly, simply using some Kodakcolor Royal Gold 100 ASA film
(rather than doing it the proper way with slide copying film and colour
filters). The results (apart from having a bit pale colours) were not too
bad, but indeed special film is needed for getting the copies right.
Regarding the 1:1 "magnification": I don't recall having had any issues with
that, but I remember there was some discrepancy with using the markings
indicated on the focusing rail...
[Joel:]
This won't be a conclusive answer but just a thought. Perhaps the close up
aberration control is useful when using the lens itself in its most
extended (close up) range. When using bellows, extension of the lens
itself is not required and therefore shouldn't be used, which would explain
Pangerl's recommendation.
This is in accordance with what Chris wrote above. It makes sense to me, so
I guess this is indeed the explanation.
[Rudy:]
hmm, wondering, cause Pangerl wrote in the same book (german edition)
that if using the 2.0/85 lens (yes not the 4/80 !) in conjunction with the
bellow you should/must use the close focus distance - IIRC - so the close
up aberrration control group can kick in.
This then, sounds strange again...?!?
I will check this again after being at home tonight (now at job place) , I
will check if what Olaf mentioned is in the german
edition (though it should but who knows ...) as in the dutch one.
I haven't checked this section again in Pangerl, but it sounds familiar...
Hmmm, anyone any idea why the 85/2 should be used at closest focusing, and
the 50/3.5 not?!?
[clintonr@xxxxxxxxxxxxxxxx:]
I'm confident that the admonition to set the lens at infinity in this
case is related specifically to it's use with the Olympus slide copying
apparatus.
This part at least seems sorted out now...
Elsewhere in this section, Pangerl indicates that the various components of
the bellows/slide copying system must be set to the index markings on the
focusing bar (rail). If the lens is focused
at any distance closer than infinity, these relationships
(body/lens/subject) would become unpredictable. (My 1977 English
version of his book does not include an exclaimation mark, but is
emphatic.)
So because of this it is best to set the lens to infinity? Makes sense, but
then it still remains weird that a lens like the 85/2 should be set to use
the close focusing group... Hmmm, perhaps the latter should be set at
infinity too then. Is there anyone (Gary? C.H. Ling?) who has actually got
"hard numbered" test data to see what the differences in quality are when
using these lenses at infinity vs. at the closest focusing distance, when
used in a bellows set-up at, say, 1:1 ?
Incidentally, the "floating" element incorportated in this and many
other designs shifts while focusing to provide optimum performance
throughout the focusing range - there is not a particular distance where
the floating element "kicks in".
O.k., that makes sense too. I seem to have remembered from previous
discussions that this group was only active at the closest focusing
distance, but perhaps I'm mistaken then...
In fact: I probably _am_ mistaken, as Tim Hughes also mentioned having taken
apart a 50/3.5, and noticing that the group moves over a significant
distance...
Secondly, I was wondering which non-macro lenses can successfully be used
on the bellows, and what their advantages might be....
Earlier in this chapter (Chapter 7: Macrophotography), Pangerl offers a
short discussion on this topic - in essence, any lens will fit, but only
certain focal lengths are suitable for use on a bellows. He advises staying
from 35mm to 135mm lenses for a variety of reasons, but notes that lenses
specifically designed for "macro" work provide superior performance when
used with a bellows.
Yes, I had read that section, and actually, reading it was what triggered
the question in me how good the results of these lenses are when compared to
the results of the macro lenses. Unfortunately I still haven't seen an
answer to that question, but I assume both the 100/2 and the 135/2.8 would
do well (I expect especially the 100/2 will do well). So, it would still be
interesting to see some comparison (or hear some experiences about such a
comparison) between the usage of such lenses on the bellows vs. the usage of
e.g. the 135/4.5 on the bellows... Anyone?
[All:]
O.k., thanks for all the replies (also the ones I did not explicitely
mention), my first question seems to be answered satisfactorily (i.e. the
mentioned lenses should indeed be set to infinity when used on the bellows),
and the second one for the moment remains open. Hopefully someone can
enlighten me a bit there too...
Cheers!
Olafo
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