At the risk of this thread already having exhausted itself, I'll have a go at
explaining the peculiar OM-F.
This camera has the ability to tell its lens electronically how to get into
focus (i.e., to extend or to retract to the correct position). However, it is
not equipped to actually drive the lens focusing motor because it has no power
supply for that purpose. Hence it does autofocusing only with a lens which
carries its own power supply. AFAIK Olympus only ever made one such lens: the
35-70mm f4 AF zoom which carries 3 AAA cells in a bulge beneath its barrel.
This lens will autofocus (AF) on the OM-F and that camera has the ability to
delay shutter release until the lens comes into focus. This is pretty neat
since you can pre-press the shutter release and wait for the lens to signal the
camera that it is in focus before it actually goes off. It even works, with
the in-focus trigger cord, for sequence shots using the winder/motor drive.
This lens can be used on other OM bodies but it will get no signals from the
camera. In this case, it becomes a power focus (PF) lens. In this mode,
focusing is controlled by two buttons (focus in and focus out) on the side of
the lens. It can also be focused manually by the usual rubber ring.
The OM-F can be used with all other OM standard lenses but it cannot autofocus
them. Olympus called this mode something like "Auto Assisted Focusing". The
viewfinder LEDs show whether the lens needs to be focussed in or out (which
must then be done manually by the operator) and also indicate when it is in
focus. I think that the in-focus shutter release feature also works.
I think that the OM-88 is a power focus (PF) camera that carries a power supply
to drive the focusing motors in PF lenses (and maybe also in AF lenses that do
not have on-board power supplies). I assume that the OM-88 does not have the
electronic circuits necessary to tell the lens what to do and that the operator
uses the power assisted thumbwheel to focus the lens himself while getting
visual feedback through the viewfinder.
Presumably, the OM-77 is a full autofocus (AF) camera that has the ability to
tell the lens what to do and also to supply it with power. It can focus itself
with no assistance from the operator. It requires AF lenses with full
electronic integration to the camera body. Olympus has made quite a range of
those.
I don't know but I guess that Olympus PF lenses will work in PF mode on the
OM-77 and that AF lenses will work in PF mode on the OM-88.
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