Fixing a Nikkor 105mm f/2.5

[Alaun]

Works as well: Put it  into a freezer and later a little heat on the outside part (just tested this a couple of weeks ago)

[Erik Lund]

Yes that is the basic idea of how it works - But also aluminum expands more than glass

Richard, What do you mean by Pitch?

[Akira]

Richard, What do you mean by Pitch?

He meant "tar", I suppose.

[richardHaw]

Richard, What do you mean by Pitch?

yes, Akira-san said it correct, black tar.

[Erik Lund]

Ok,,, next question; What do you mean by Black Tar?

[richardHaw]

Ok,,, next question; What do you mean by Black Tar?

Black tar is basically the black liquid goo that careless dinosaurs step into, leading to their death

[Erik Lund]

OK, and where do you apply it if your not prehistoric?

[Akira]

The pitch or black tar is used to fix the lens to the rotating platform when they are ground.  Perhaps it is also used as anti-reflection paint and applied to the edges of the lens elements?

[Erik Lund]

Thanks,,,

But it still really doesn't make any sense to me

Flat black paint is used for the glass edges and the rear opening on some lenses,,,

[Akira]

Well, I was just guessing its use as anti-reflection method.  But tar is pitch black!

[Erik Lund]

 

[richardHaw]

Hello sorry for not being clear 
some lenses have it to glue it with its casing. i was shown once where it was baked to separate it from the glass. i asked and i was told "pine sap" basically pine resin. the reason thy probably use this is because it is pliable when warm. according to the repairman, telescopes use this more than camera lenses. i guess this is an old technique

[Thomas G]

*sigh, well, the Utrecht event came close and I had to hurry.
Thus I did not take as many photos as planned.

Bringing the f-stop klick spring back.

[Thomas G]

moving on. Putting little screws back in places.
Carefully following the notes taken on the protective sheets of (news)paper.

[Thomas G]

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