On Sep 6, 2005, at 3:32 AM, mike wilson wrote:
A D-FA50 macro lens is designed to be best at flat-field imaging,
stopped
down to f/8-f/32, in the near-focusing range. An A50/1.4 is
designed for
general pictorial use at wide apertures, and will not perform at
its best at
copystand distances.
It was either in the general Pentax lenses and accessories booklet or
the manual of the 1.7x AF T/C that I read that the 50/1.7 is
recommended for macro work with extension tubes; the 1.4 was
recommended against.
IIRC, that was deduced to be due to the flatness (or lack of) of
the focus plane.
Yes. I've tried both lenses (A50/1.4 and A50/1.7) and the f/1.7 model
definitely outperforms the f/1.4 in flatness of field at macro
distances. Neither can compete with a dedicated macro lens but they
do fairly well nonetheless.
Godfrey
