In article <5enkp8$752@rock.me>, weage@mtu.edu says...

> I just managed to get my 200/f3.5 lens fixed. However,
>when I was working on it, I noticed that when the filter
>was in place, it didn't focus to infinity correctly.
>When the filter was off, the focus was correct, but adding
>the filter made my focusing screen slightly fuzzy.
> Do I have a bad filter, or is it because the filter
>has a slight oil film that I haven't been able to remove completely?

You have a bad filter - oil could make the image slightly
"fuzzy", but would not change the focus (and since you have
attempted a cleaning, there is probably not enough oil residue
on the filter to affect image quality significantly...). If the
filter had a slight (but pure) "power", it would slightly change
the effective FL of the lens/filter combination (and therefore,
infinity focus) but should not affect sharpness (if proper
focus can be attained). Most likely, the filter has an
irregularly curved surface, making it useless for
anything but soft-focus work (if you can see
the filter softening effect in the
finder, it is B A D...;-)
Hope This Helps