At 08:28 29.1.2001 -0600, you wrote:
>
>Wieland wrote:
>>Dan Scott wrote:
>>> My favorite general purpose lense is an FA 35/2 AL, although I just
>>> acquired an A 50/1.7 to use with my bellows.
>>
>>This is an important comment. If I remember correctly, the bellows manual
>>says that the
>>50mm 1.4 and the 1.2 lenses are not suited for the bellows. I don't know
>>why, but maybe
>>one should take that into consideration.
Propably the reason is that in designing fast lenses, more tradeoffs are
made regarding flat field of view than has to be with less fast lenses.
After all, most photography happening at that 1.2 or 1.4 aperture is of
people and 3-dimensional objects, so flat field doesn't matter so much.
Also, they might be optimised for some subject-film distance, so they might
perform badly under closer distances (just a wild guess here, as this
doesn't happen much with prime lenses. Only with zooms, performing nice at
infinity but ugly at the closest focus)
What I found to be among best lenses for bellows use (and not only in my
opinion, but others!) or extension tubes use are simple Tessar formulas.
These were actually formulas of some of the Pentax's own Macro lenses, If I
remember correctly.
These give very flat field of view and high contrast and sharpness, when
stopped down to middle apertures (as their maximum aperture is 2.8 or
lower, 5.6 is often enough). A friend tested one tessar type from USSR as
among his best lenses at macro work! (but it came from USSR, so quality was
wildly jumping up and down - from the three he tested only one was great,
others just "mediocre" for tessars)
Also, Tessars are used for most medium-price enlarging lenses, and perform
well at it.
BTW, anybody actually _tried_ reversed wide angle for macro work? If not
reversed, most SLR wideangles just suck at macro, but reversed might be
better. They also wouldn't lose so much light to bellows factor (which is
valid only for normal construction lenses. It's more for telephotos and
less for SLR wideangles).
I have an idea for a perfect wideangle for macro but still working on it.
Frantisek
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