35-105 3.5 Canon FDn focusing problem

[Darkroom317]

I have 2 35mm-105mm FDn lenses that focus at 105mm through about 50mm but do not focus at 35mm. The microprism does not match up at 35mm. One of the lenses is also having problems throughout the entire range. Is this common and where can I have these lenses serviced if need be?

 

[flatulent1]

Never heard of this problem before. If two lenses are having the same problem, I would suspect the camera. You've tried both lenses on more than one body?

 

[Darkroom317]

Never heard of this problem before. If two lenses are having the same problem, I would suspect the camera. You've tried both lenses on more than one body?

Yes, two different bodies.

 

[Darkroom317]

bump*

 

[Nicholas Lindan]

By this, do you mean that you have to refocus the lens as you zoom from 50 to 35mm?

 

[andrewc]

Mine doesn't quite line up at 105mm when I try to focus to infinity. The pictures still turn out to be quite sharp though, and it seems that it lines up just fine throughout the rest of the range.

 

[2F/2F]

Mine doesn't quite line up at 105mm when I try to focus to infinity. The pictures still turn out to be quite sharp though, and it seems that it lines up just fine throughout the rest of the range.

Since the pix are sharp when focus is set at infinity, but the viewfinder image is not, my first guess is that the focusing screen is not properly seated. My second would be that the mirror is not sitting in the proper location. (I had the latter problem with one of my first-generation F-1s.)

 

[Andrew K]

This is not that uncommon a problem, and there could be several causes.

The lens that will focus from 50-105 - I would suggest that infinity needs to be readjusted at the wide angle lens. This is done by removing the rear lens mount, and then replacing/adjusting the spacing washers at the rear of the lens that adjust infinity focus. In the old days you could buy washers of dirrerent thicknesses - now you usually pack them out with home made washers made of aluminium or brass..

The other lens - do a little test for me. Set the lens to 50mm, and focus an object say 10-12 ft away. Now zoom the lens to 105, and check if the object stays in focus. Now zoom to 35, and check again. Finally set the lens to 50mm and check it is in focus, then zoom to 105 and back to 50, and see if it stays in focus. Then zoom from 50 to 35 and back and see if it stays in focus...

I suspect the zoom guides will be worn (the zoom giudes have a plastic coating on their outsides - they are made of brass) - when the plastic wears the lens will not stay in focus when it is zoomed...

Any camera technician who has a lathe and some time can turn up new guides, and make new focus shims to adjust the focus..just a matter of finding someone who has done it before and is willing to do it..