Recently Wieland Willker wrote:
>
> Thanks Boz for your patience,
No, problem. The A 1002.8 is my favorite lens, so I will gladly defend
it...
Your understanding of the working distance is correct. The thing is that
the FREE macros change their focal length but they also change the
positions of their nodal points, so that the working distance at 1:1 of the
FREE lens is longer than the working distance of a 60 mm lens put on tubes.
Semd me an e-mail to the pentax-k address, and I will measure the
lens-to-image distance for a few magnification ratios.
Note form the KMP that the focusing distance (film-to-subject) of the FREE
macros is 310 mm, but of your 50 macro it is only 190. There is a
difference in the length of the lenses when they are set for 1:1
magnification, but it is not as big as 120 mm.
So, the final effect is like this: the focal length becomes smaller and the
lens-to-subject distance does too, but not quite so fast. So the effect is
like using a lens with a focal length of 60 mm but with lens-to-subject
distance of something like an 80 mm lens.
Note that the same happens with the 200/4 Macro.
Cheers,
Boz
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