On 2011-12-23, Michael wrote:

That kind of aperture setting was called "pre-set" as opposed to "auto"
(the aperture stayed wide open during framing and closed down to what
you set it at when you took the picture, doing so "automatically").
These lenses were very common in the 1960s and even the 1970s as low
cost alternatives to the "auto" lenses. I think they started to
disappear when lenses became automatic in the sense we think of them
today.

Old lenses were manual only (and of course rangefinder cameras did't use
automatic diaphragms for the most part), then you had pre-set lenses,
then you had semi-automatic lenses, then you had automatic lenses.
Semi-automatic lenses closed the diaphragm when you took the picture,
but you had to reopen the diaphragm after the shot. Pentax Auto Takumar
lenses always (I think) had a manual/automatic switch that you could
flip to have a completely manual lens to use on old cameras. Newer model
lenses often lack the manual/automatic switch. These tend to come from
the off-brand companies like Vivitar.

Bud