Canon FD 80-200 F4 L - Resetting infinity focus?

[Zack Birlew]

Hey, everybody, I recently lucked into a fixer upper of a Canon nFD 80-200 F4 L that was quite the experience to take apart completely for fungus and oily aperture blades, now I’m resetting focus and having problems. I try to not put a fungus infected lens on my camera so I’m not sure if it was like this normally as a quirk but I can seem to get infinity only either at 80mm or at 200mm but not both. For those that don’t know, the back focus is similar to the 35-105 3.5 that I’ve posted about before with 5-6 screws near the back after unscrewing the zoom scale tube but on the 80-200 4.0 L, the back focus seems fool proof with two silver shims and after making markings upon initial disassembly, things seem to line up no matter what, unless I’m mistaken. The front focus is adjusted by unrolling the rubber focus grip and removing the taped clear wrap underneath to undo two roller screws and twisting the front cap off where the helicoid is. Now, I can get it to infinity focus at 200mm and have the ability to do infinity focus at the 3 mark at 80mm but I would think that is pretty off. The only thread I’ve found online talked about this quirkiness with DIY infinity focus adjustment but then I’m not sure Canon would have sold an L lens like this. I could be wrong and this could be totally normal but I wanted to ask if anybody here had any knowledge or advice to help?

 

[Zack Birlew]

Update! Since I didn’t hear word back, I’ve decided to leave the lens as it is since I can technically achieve infinity focus at least, despite being in different spots on the focus scale. It’s a nice lens and I can see it being useful for when I want that Canon FD look but I don’t see it being all that different quality-wise from some of my other Canon FD zooms, despite the L branding. The only other thing I can think to try is readjusting the back focus at 80mm and see if that balances things out on the focus scale but, again, if anybody has any experience or advice about this lens, please let me know. So far, infinity at 80mm is at 3 and infinity at 200mm is on infinity exactly, if that’s correct, then I’ve got it right, if not then please post a reply or send me a PM.

 

[Zack Birlew]

New update! So, I happened upon another 80-200mm nFD F4 L that had some fungus/haze issues on the front elements and decided to give it a shot at cleaning and repairing it since it was another inexpensive find. I made sure to check the rear elements which seem to be dusty but otherwise fine, all the bad stuff is on the front with this sample, and mounted it on my A7S to see and the lens does indeed turn out to be parfocal! My normal infinity spot is a telephone pole far off in the distance outside the window of my room and I could see that it was in focus slightly before the infinity mark and it held from being fine tuned at 200mm to 80mm and back. I haven't taken it apart yet to clean, I may make a repair video out of this, and I'll be sure to take extensive notes of what I see on this sample and, if successful, whether I can replicate the results on my first copy to see if I can get things back in order for both lenses.