Hello, I'm new to the group.
What is the difference between the OM4 and OM4t/i?
I have a OM4 myself.
Material (?)/finish of top and bottom covers. (It's not "t/i", but "ti", for "titanium").
And the ability to do FP-flash using the appropriate Olympus flash unit ("ti" has, plain hasn't).
OM-4 had a reputation of eating batteries, so OM-4T has an updated circuit board.
OM-4 could use the T series flashes in TTL mode while the OM-4T could also use the F-280 flash in Super FP mode for synchronization at any shutter speed up to 1/2000. I like the Champagne color on my OM-4T.
Some OM4s actually have the improved, battery saving circuity mopar_guy mentions. Put the camera in battery test mode and if it shuts off after a minute or so automatically, you have the newer board.
this is a very good link for the OM groupies. http://olympus.dementia.org/
The seals were also improved in the Ti models. The top plate is just a touch taller in the Ti models to accomodate the better seals.