> Have you ever compared the results of
> the micro lenses (55, 60, 105mm) and
> the normal lenses fitting on the extension
> tube?
Yep.
> What's the difference?
You don't have to stop the macro lenses down as
much when copying a flat subject like a photo or
document -- they're corrected to provide a flat
focus field.
I use the 55 and 105 AI-S macros -- the 55 stays
flat at all distances, but has noticeable pincushion
distortion at infinity. The 105 is only flat at it's
minimum focusing distance, but it doesn't have
noticeable distortion at any distance.
> Which can produce the best result?
> I am so curious if I really need to
> get a micro lens.
If you want to copy flat subject matter, the 55mm
or 60mm will be worth their cost.
If you want to photograph 3-dimensional subjects,
you don't need a macro lens. A short telephoto
(85mm - 135mm) on extension tubes will produce
images just as good as the 105 macro, and superior
to those made with a 55 or 60 macro (because the
shorter lenses distort perspective at small camera-
to-subject distances).
The longer macros are still nice to have. Swapping
extension tubes every time you change the
camera-to-subject distance becomes tedious.
-Don
