Moving front element

[Zang]

Hey all,

I am overhauling Contax Zeiss 85mm f2.8, initially wanted only to remove internal dust and regrease the helicoids. When I took the lens apart, I notice that the very front element is rattling a bit when I shake the front assembly. It is not too bad but it is definitely rattling. Now, I am very sure it has been like that since it left the factory. There was no indication that anyone opened the lens up. Of course, I want to tighten the element. However, the front assembly housing is so difficult to unscrew. My question is, could it be a serious optical issue if I leave it as is?

I will still try opening it, but it seems to be next to impossible

Cheers,
Zang

[Zang]

Nail polish remover + patience did the job! Chemical nor patience alone will not work We need both.

I have learned one thing working with lenses, never lose the hope

[Toby]

Hey all,

I am overhauling Contax Zeiss 85mm f2.8, initially wanted only to remove internal dust and regrease the helicoids. When I took the lens apart, I notice that the very front element is rattling a bit when I shake the front assembly. It is not too bad but it is definitely rattling. Now, I am very sure it has been like that since it left the factory. There was no indication that anyone opened the lens up. Of course, I want to tighten the element. However, the front assembly housing is so difficult to unscrew. My question is, could it be a serious optical issue if I leave it as is?

I will still try opening it, but it seems to be next to impossible

Cheers,
Zang

Lens elements are very precisely placed to achieve the designers' aims. It certainly will decrease performance, but how much is another question. I have, as an experiment, increased element spacing in some old vintage lenses by partially unscrewing front or rear element groups. A small amount will probably not be noticeable, but it depends on the design of the lens. In my experiments I noticed a definite increase in spherical aberration when spacing was increased.

[Zang]

Thanks Toby,

That was my feeling too, thus my question. In my previous lens (Canon 135mm f3.5), I had a moving element that I identified fixed at the end, but before I found that, test pictures look more than OK.

Luckily, I was able to open up the front assembly of Zeiss 85mm, clean up all the thread lock and assemble everything back again. Now I feel I can tighten the casing nicely with consistent but not too hard resistance. I think the way the spacers and barrels were designed ensures the glass elements to be well aligned when sited firmly in their slots so I am pretty sure they are OK now.