Canon FD 85-300/4.5 SSC. Loosing focus when zooming.

erog_011263 · Joined: 16 Jun 2013 Posts: 3 Location: Trondheim, Norway

I just bought a Canon FD 85-300/4.5 SSC with a problem.
At 300 mm infinity focus is OK. Zooming out to 85 mm gives 'infinity' focus at about 20 meters.
The zoom and focus rings feels dry, but tight, so I don't think there is anything broken. Someone suggested the problem could be fixed by changing the lens-to-flange distance (Canon FD 35-105/3.5). I took off the rear mount, but couldn't see any obvious way of doing this on this BL mount. And I think this would mean the lens has to get closer to the camera?
Any good advice on where to start?
Some possible adjustment points: Around the front lens group there are four screws, and the rear lens group can be unscrewed from the rear...
I have some experience repairing Canon FL/FD lenses, but not with this problem.

-Egil

philslizzy · Joined: 07 Aug 2012 Posts: 4748 Location: Cheshire, England

Some zooms do change focus when zoomed (technically a varifocal lens). If you focus on infinity at 300mm then come back to 85mm can you re-focus to infinity? A zoom that keeps its focus is called a parfocal lens.

visualopsins · Expire: 2025-04-11

Welcome Egil!

I think you are correct, that lens needs focus adjustment. If nobody here can help with sequence of steps, perhaps a guide for another similar zoom will help. Some guides I have seen involve disassembling the lens helicals, then re-assembling & adjusting the inside helicals, then adding & adjusting the outside helicals at either end of range of travel. Basically, this procedure sets the ratio of travel between the helicals so parfocal is obtained. The helical screws are probably for adjusting the outside helical only.

Here's hoping somebody has the info you need!

Himself · Expire: 2013-05-30

Wait for Trifox to chime in. He's the expert in those FD thingies.
Or email him.

erog_011263 · Joined: 16 Jun 2013 Posts: 3 Location: Trondheim, Norway

trifox · Expire: 2014-05-29

I am afraid that the lens is 'OK'

Well, I can't see the reason why the short end shouldn't go to infinity

I have had FD 50-300 L - I couldn't get the infinity at the 50mm end

Crazy but true..

erog_011263 · Joined: 16 Jun 2013 Posts: 3 Location: Trondheim, Norway

hangard · Posted: Mon Aug 19, 2019 1:58 am Post subject: Old thread, but new information

I know this is an old thread, but so are all of these lens Wink

erog_011263, did you get the focus on this lens to work?
I have the FL 85-300 F5 that looks like new! Seems the reason it is 'new' is non use due to not having infinity.

After reading this post I fixed mine.

loosen (remove) set screw on the focus barrel now it will not stop at minimum focus, keep turning a little bit.
as soon as the infinity focus stop is visible loosen the two screws, move to more focus, tighten the lock.
turn the focus back to some long distance and replace the set screw.

This was enough to give Infinity and a bit beyond and new life to this lovely albeit heavy lens.