I used the A24/2.8 zone-focused very successfully on my trip, but
found the A50/1.4 to be too long for much success in zone focusing.
Which meant that, in evening/low-light street conditions, the
FA135/2.8 was a better fast prime to work with as it was quicker to
AF than to manually focus the 50mm, despite the A50/1.4 being faster.
Now I'm using an F50/1.7 and finding it to be an excellent lens for
this purpose. It has no trouble focusing in lighting similar to the
photos you presented on the DS body.
Bojidar documents the KAF vs KAF2 lens mount, which is essentially
the difference between F and FA series lenses.
http://kmp.bdimitrov.de/technology/K-mount/Kaf.html
http://kmp.bdimitrov.de/technology/K-mount/Kaf2.html
In practical usage, I don't see the FA version as having any hugely
important features lacking in the F.
Regards 50/1.7 vs 50/1.4, the A/F/FA lenses are optically identical
for each maximum aperture design. I have A50/1.7 and F50/1.7 lenses,
as well as the A50/1.4. The differences are:
50mm f/1.7:
- sharper wide open
- better in near-focus due to better flatness of field
50mm f/1.4:
- very smooth OOF rendering between f/1.4 and f/5.6
With both lenses at f/2 or better, sharpness/contrast between them is
virtually indistinguishable. Only the very small difference in
rendering is different, and you have to really know what to look for
to see it. I'm sticking with my F50/1.7 for the present.
The FA50/1.4 seems to be available in limited supply every few weeks
at B&H, costs $210 new. I haven't seen any used examples around
recently. I bought the F50/1.7 as NOS (in the box, unused) and it
cost me $134, about three dollars more than the A50/1.4 did. The
A50/1.7 was a lot less expensive.
Godfrey
