Opening middle lens group of Nikkor AF 300mm f4

Dinis · Apr 25, 2024

Hi all,

I was wondering if anyone had any ideas about how to open the middle lens group of this lens to clean out some fungus. I’ve tried soaking the threads with acetone and lighter fluid. I’ve also tried heating it up with a hair drier. It doesn’t want to budge. Any ideas?

Many thanks!

Andreas Thaler · Apr 25, 2024

Dinis said:
Hi all,

I was wondering if anyone had any ideas about how to open the middle lens group of this lens to clean out some fungus. I’ve tried soaking the threads with acetone and lighter fluid. I’ve also tried heating it up with a hair drier. It doesn’t want to budge. Any ideas?

Many thanks!

I recommend talking to Michael @forest bagger about this, he is an expert in repairing Nikkors.

forest bagger · Apr 25, 2024

Usually I try it the same way - acetone and hot air - and then it is the question whether the ring which holds the single lens has notches for the tool (then use the tool) or not (then use the rubber prop) to remove the single lens.
Some times both won't work, so you have to use a hammer and a small chisel to drive the ring off.

Christiaan Phleger · Apr 25, 2024

I'm just astounded as to why the heck would this area have fungus in the first place, and the fact that it's very difficult to even access that section I would have thought that it would be too tight for anything to grow. Good luck with the repair, those solutions are likely good ones.

Dinis · Apr 26, 2024

Thanks to everyone for their suggestions! This group is quite stubborn to get apart. I’ll keep trying.

forest bagger · Apr 26, 2024

I am surprised that this lens group has fungus.
Are you sure that there is fungus, and not a clouding in the cement which holds the two glued lenses together?

Dinis · Apr 26, 2024

Yes, I can see quite a bit of fungus spidering inside. Unfortunately, there was fungus on almost every lens element in this lens.

forest bagger · Apr 27, 2024

Dinis said:
there was fungus on almost every lens element in this lens.

So that was a Nikon AF 300/4 Nikkor full of fungus - how could this have been happened?

Dinis · Apr 27, 2024

Not sure, I took a gamble on a “not tested - no returns” lens on eBay at a cheap price. My fault ….

Opening middle lens group of Nikkor AF 300mm f4

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