Hello,
My first post on APUG, here goes. I have a Nikon F2 w/your garden variety Nikon 50mm f2.0 manual lens. It works great, but when I focus, the image seems to shift slightly. Should I send it in for a tuneup, should I be worried, should I not worry about it, could it be something serious?
Thanks

How do your negatives appear? Sharp?

Sounds like something loose in the lens. Could use a tightening of some screws. Take it to a professional.

Thanks, will send to the shop, it does make sharp pictures.

I've noticed this, too. Perhaps the focusing helicoid is a bit loose, which could cause focus shift at large aprtures. It doesn't seem to be a problem at the moderate apertures I use. Repairing the lens might cost more than replacing it.

.... Repairing the lens might cost more than replacing it.

This is a good point.

Sadly, nowadays you can find a Nikon manual camera for very cheap on eBay usually serving as a back lens cap for an attached 50mm/2.0 (and sometimes even a 1.8!). :(

Yes,
I guess I could buy another, and just be sure to ask the seller if the image remains stable during focusing. Thanks for the suggestion.

I have a 50mm 1.4 that does the same thing, a little annoying but causes no problem. Probably just a little slop in the helicoid.I would personally just leave it and carry on regardless especially if your shots are sharp.
Tony

... Probably just a little slop in the helicoid....

This conjures up some rather disturbing imagery...

Gross!!

Check to see if all the screws in the lens mount are tight, if they're not you would have focus shift. There could be as few as three or as many as six depending on the lens.