Diopter Dial - Whats it for ?

My Olympus C-900 Zoom has a Diopter Adjustment dial.

What is it for... when is it used ?
The operating instructions don't give much of a clue. Adjusting
the dial doesn't seem to make a difference as far as I can see.

Thanks

 

I'm not familiar with that particular camera (I'm a Minolta man), but
I'd assume that this dial is associated with the eyepiece. (My more
recent cameras have this feature.) It'd be to correct for poor
eyesight, so that spectacle-weareres (like me) can use the camera with
their glasses off. I'd expect a correction range from something like
+3 (moderate long sight correction) to -3 (moderate short sight
correction). (For older cameras, like my Minolta X-700 and XD-7, it's
common to buy separate correction lenses which clip onto the
viewfinder.)

Peter.

 

The diopter dial compensates for bad vision. I use it when I don't have my
contacts in and I'm using manual focus. What's in focus without my contacts
won't be to everyone else.

 

John,
This is a pure guess but... If the diopter adjustment dial is anywhere near
the viewfinder, then it probably adjusts the viewfinder focus to allow for
individual eyesight capabilities.
HTH
Tim S.