Here is what I have found out about the 105mm f2.5 lens...
1959 Type F - 5 elements in 3 groups and 9 or 6 shutter blades
1971 Type F - 5/4 and 7 shutter blades
1973 Type C - 5/4 and 7 shutter blades
1974 Type K - 5/4 and 7 shutter blades
1977 Type Ai - 5/4 and 7 shutter blades
1981 Type Ai-S - 5/4 and 7 shutter blades
Mine is Type F (mid/1960s) with 5 elements in 3 groups and 6 shutter blades. The coated lenses were Type C starting from 1973. The pre-1971/2 lenses were Sonnar design and from 1971/2 Nikon used a Gauss design (5 elements in 4 groups). Note: some sites claim that there is no difference in the optical design with the 105mm from 1959 to 2005??? The multi-coating started from 1973.
On a small technical note, the original 1959 lens had a 180 degree focus throw which was reduced to 170 and then to 140 degrees with the Type Ai-S in 1981. My understanding is that in general, autofocus lenses have a much reduced focus throw.
Some photographers report less contrast with the old non-Ai lenses but better out of focus rendering(?). I can only surmise that the contrast is impacted by the lens coating, glass formula, film, exposure (duh), etc. These images were taken on a bright day in a partially shaded park. My personal experience is that the non-Ai lenses give more contrast... but maybe that's just me.
A comment about non-Ai lenses on an F3 body: to mount the lens you have to flip up the index tab. This is a physical communication between lens and body regarding f-stop and is used in metering (the feature is not available with non-Ai lenses). This step is only required when you mount the lens. Once the non-Ai lens is mounted on the F3 body I can expose in (1) manual or (2) automatic mode. To use the meter you must depress the DOF button (stop down metering), therefore (1) set shutter speed, focus, depress the DOF button for metering, re-set the shutter speed & aperture as necessary, and shoot -or- (2) set A-mode, focus, depress DOF button and shoot. So in Auto-mode it's just a matter of remembering to press and hold the DOF button when you shoot
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Ai = auto indexing
Casey
