In article
>I'd like to take advantage of the collective experience in this
>group to decide which close-up accessory will likely give me the
>best results in photographing wildflowers.
>An extender tube will not introduce more elements into the
>optical path, but will force a lens into a focusing range for
>which it was not optimised, and in which it may not produce
>sharp images. Light scattering within the tube may as well
>degrade contrast.
>Diopter "filters" will not have these problems, but will
>introduce another element (or presumably two for an
>anchromat) into the path.
>Is there a consensus (what, here?) on which alternative will
>generally yield the sharper images, and just as important,
>the images with the less jarring out-of-focus highlights?
I think there is no answer to this (as I think you realize).
Which works better (I would eliminate the single-element
close-up lens, so, I guess, there is an answer to part of
the question), the tube or the achromat, depends on the optical
design of the lenses they are used on. (Though, most anything
will work with the lens set to about f16.) I have found the
achromat that is made for the Sigma 90mm macro (it is available
from Sigma for about $35) works very well on some lenses (when
the lens is stopped down) that are normally poor at close focus.
You can only try both on the lenses you have and decide for
yourself which works better (if you are using Nikkors, I have
tried zillions [a technical term] of combinations, and may be
able to help you with specifics). As far as the appearance of
out-of-focus highlights, the same applies - you will need to
try a combination to see what happens.
Hope this helps.