Canon FD 400mm f/2.8L Protective Glass Problem

I've discovered that my Canon FD 400mm f/2.8L has a bit of spidery fungus that started growing between the two front pieces of protective glass. The rest of the lens is clean and I've taken precautions now by removing the front protective glass from the lens--both elements basically screw in to the front like a giant double protective filter. Add some UV light and I think the rest of the optical elements are safe (though I need to re think storage now...)

Anyway...the problem is that fungus is between the two protective elements. There's a small indent that looks like evidence a seam where they actually unscrew from each other, but I'm not sure about that and cannot get them to budge. Perhaps they're screwed and glued, too, and I need some acetone to separate them?

Or perhaps I've finally encountered a lens problem that I simply cannot solve on my own...

If anyone knows more or has a suggestion, I'm all ears.

Nail polish remover/acetone on the threads will no hurt so give it a try.

Be sure to look for a grubscrew somewhere locking the two threaded rings.

Looks like the EF version was built the same way. This might be useful: http://f20c.com/stuff/canon/partslist/EF 400 2.8 L USM.PDF

E. von Hoegh said:

Be sure to look for a grubscrew somewhere locking the two threaded rings.

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I'll keep that in mind, but I haven't seen anything so far. I won't have time until this weekend to look more closely...

EdSawyer said:

Looks like the EF version was built the same way. This might be useful: http://f20c.com/stuff/canon/partslist/EF 400 2.8 L USM.PDF

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That basically looks identical to what I'm dealing with. Edit: actually completely identical across the board for the whole lens. Looks like the original EF 400mm f/2.8 was optically the same as the FD...just like they did with the FD 300mm f/2.8.

So they do screw a part. Assuming that's correct and there isn't a grub screw or glue, I might just need a strap wrench to unscrew them.

Thanks!

MAubrey said:

I'll keep that in mind, but I haven't seen anything so far. I won't have time until this weekend to look more closely...

That basically looks identical to what I'm dealing with. So they do screw a part. Assuming that's correct and there isn't a grub screw or glue, I might just need a strap wrench to unscrew them.

Thanks!

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Be careful with that strapwrench, they do not all apply perfectly symmetric force. Try a rubber-sheet jar opener first, after you let it soak with acetone for a while - maybe a couple applications. Good luck.

E. von Hoegh said:

Be careful with that strapwrench, they do not all apply perfectly symmetric force. Try a rubber-sheet jar opener first, after you let it soak with acetone for a while - maybe a couple applications. Good luck.

Click to expand...

At the moment, I don't have a strap wrench or a rubber sheet jar opener. I'll do a few acetone applications, try by hand and then if I'm stuck, I'll pick up a jar opener.

Thanks for the warning!