The OM4 and Ti have a small plastic pin which protrudes from the lens mounting
flange. The pin is a switch which resets spot readings and the memo function
if a
lens is removed. Some non Olympus lenses, including certain Tamron adaptall
mounts,
have a fourth screw hole which can pass over the pin when lenses are mounted
and
removed. Both the hole the screw is recessed in and that for the pin have
sharp
edges. The result is a very effective guillotine action which can shear off
the top
of the pin so that the switch is no longer depressed when a lens is mounted.
This
will nobble the spot metering function of a 4/Ti - don't know about the 3.
Filling in this fourth hole with epoxy apparently prevents the problem from
occurring.
The OM2s has a program mode which the 4 lacks. The 2s has continuous spot
metering
in manual mode only so effectively is single spot metering except for those
agile
of mind who can average several readings in their heads. The 4 can average
meter in
both manual and auto modes and take spot readings in both. Up to 8 spot
readings
can be made and the 4 will average them. The 4 has Hi-light and Shadow buttons
which provide pre-set levels of compensation to render a spot metered area
black or
white. The 4 also has a memo function which can store a given exposure so
multiple
shots can be made with the same exposure.
The can achieve 5 fps with a motordrive while the 2s is limited to 3.5 fps
The viewfinder displays are different.
The 2s has an X rated shutter sound.
Giles
Jeffrey E Bellin wrote:
> I've seen a lot of talk about a problem with non-OM lenses and the OM-4
> body. Something about a pin that can be broken? Is this a problem with
> the OM-4t and the OM-3 also?
> Also what are the main differences between the OM-4 and M-2s. I've heard
> they have pretty much the same electronics. What did Olympus do to beef
> up the OM-4?
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