Zuiko zoom focus?

[Gerry M]

I have a Zuiko 75-150/f4 lens that, I think, has a focus (?) problem. In the vf, all seems good until infinity. Then the split image won't quite line up; there is still some misalignment. The few photos that I have taken with it seem to have been in focus. Can this be a screen problem? I have tried it on: OM-1, OM2n (x2) bodies, all show the same image in the view finder. Anyone have this experience?
Thanks,
Gerry

 

[Paul Sorensen]

I am not sure if this might be related to your issue, but split screen rangefinders can be difficult to use with lenses as slow as f/4. I would just expect to see part of the split dark, however, and not out of alignment, so this might be completely unrelated. Oh, one other thing, what aperture are you shooting at? If you are shooting at f/8 or above, you might just be seeing the increased depth of field, so the lens could actually have some sort of issue in relation with the finder.

 

[Gerry M]

Paul, Thanks for your input. The problem occurs all the way to f4, and it is misalignment of the image. Held either vertically or horizontally, the vf will show some lack of co-incidence. I seldom use telephoto on the OM's, as to me, it sort of defeats the purpose of the small body.

 

[mr rusty]

I think I *might* have an explanation. I have one of these as well, and when I got it there was "fog" on the inside of the second element - (it was cheap), but it wasn't fungus - it looked like oil condensation. I have heard of other 75-150s with the same problem. I discovered that the front elements are mounted in a screw in ring exposed by removing the hood (the hood bit unscrews), which is secured by three lock screws. When the lock screws are undone the front elements can be removed for cleaning - I did this and got rid of the "condensation" easily, however, what I found was that the screw in ring wasn't screwed in all the way - it is obviously set to collimate the lens to infinity focus, so I guess its possible someone has had yours apart and messed up the collimation. I might be totally wrong, but it's a thought!

the parts diagram is here http://olympus.dementia.org/Hardware/PDFs/75-150mm_f4.pdf. The first 5 parts are a unit built into the 3rd part from the front. This unscrews from the 9th part when the set screws are removed.

bit on collimating here http://elekm.net/zeiss-ikon/repair/collimate/ although I just set mine to align at infinity and its been OK. Its not an expensive lens, so worth a try maybe?

 

[Gerry M]

mr rusty,
Thanks for that info. I think that may be where the problem lies, not condensation, but maybe a loose element. I'll give it a go, as it is not a valuable lens, by any means.
Gerry

 

[mr rusty]

I think you'd hear a loose element rattle. I am sure you will be able to tell if the lens has been apart when you take the hood off. The little setscrews are very small and difficult to get out. If its been apart I bet they are chewed. If you can loosen them, just try turning the front assembly and see if you can bring infinity in to line. The focussing mechanism only moves this assembly in and out - nothing else, so you can't really mess the lens' useability up by screwing the front element assembly in and out - its what the focus ring does anyway.

 

[Gerry M]

Thanks to your input, I have the infinity focus set now. Strangely, the set screws for the front element had not been loosened. They were still set in the clear lacquer (?). I loosened those and screwed the front assy in ( a tiny bit ) until the split image coincided at infinity. I do appreciate your help.
Gerry

 

[mr rusty]

glad to be of help