My eyes are dim, I cannot see....

[Retro-Grouch]

And another thing: do you have astigmatism? Astigmatism that is uncorrected by the diopter lens might account for the one diopter discrepancy.

I do, although it isn't severe; I never thought this might be an issue that would influence diopter choice. Perhaps it does. Thanks for that tip!

 

[Malcolm M]

It's high time the OP replied to this thread...

CLAdictic- I don't think I have cataracts (yet). My vision is perfectly clear, just the focusing helical is jammed on infinity.

The tip about correction lenses from the FM range is useful. That should give more search options. I have checked, and F2 and FM2 eyepieces are interchangeable. The problem is the F, where all this started. I can't seem to unscrew the eyepiece by hand, even to the extent of drawing blood. It's the earliest version of the TTL metering head, so probably hasn't moved in nigh on 60 years. Or is it not interchangeable?

Solution- don't go to sixties weekends, and don't use a 35mm f2.8 (hardly a lens which snaps in and out of focus).

 

[lxmike]

Have you tried Grays of Westminster in London, superb service and a great catalogue of stock.

 

[Malcolm M]

Eyepiece correction lenses for the FM seem relatively common. The currently fitted lens looks like it should be removable, but as stated above, I couldn't shift it. I'm deeply reluctant to use Mole drips or similar. Maybe I'll just have to live with it.

 

[Retro-Grouch]

Eyepiece correction lenses for the FM seem relatively common. The currently fitted lens looks like it should be removable, but as stated above, I couldn't shift it. I'm deeply reluctant to use Mole drips or similar. Maybe I'll just have to live with it.

I've had similar problems with other cameras. I used the tiniest drop of WD-40, applied with the tip of a needle at the edge of the threads. Let it sit a while, then get a good grip with a fat rubber band and have at it.
I wouldn't normally put WD-40 and a camera in the same room together, but sometimes a man's gotta do what a man's gotta do... I suspect that the frozen eyepiece is the result of sweat getting in the threads at some point. Very corrosive stuff!