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Re: [Rollei] Why the 6-element lens for 3.5Fs

Richard Knoppow wrote:

>    You do not need to dismount the glass to clean it. Just
> clean both surfaces. I don't know how Hassy lens mounts are
> made but 35mm camera mounts often have retaining rings to
> hold the back elements or groups in place. These rings don't
> always have slots or dots on them, they are removed by a
> tubular friction tool. The frustrating thing is that I could
> probably figure it out in a few seconds if I had one to look
> at.

On the back of my lenses, i found two concentric retaining rings, each with
two pin-plier holes. And, closest to the actual glass, a semi-circle ridge
with two slots opposite each other.
Removing the inner of the two retaining rings (screwed off), the rear lens
group assembly (including semi-circular ridge) appeared to be loose. But
just a bit. It can be turned (inserting an appropriate "something" in the
two slots in the semi-circle ridge), clockwise and anti clockwise. Yet it
doesn't appear to screw out, or in. It just rotates. It doesn't (or not so
that i have noticed) with the retaining ring in place.

I have tried lifting the group assembly out, but it wouldn't budge. There is
very little purchase on the semi-circular rim anyway. Maybe if i could get a
better grip? Maybe it isn't meant to lift out?

And that's as far as i got.

That is: i found that removing the other, outermost retaining ring allows
the complete lens group to be taken out of the focussing mount. Good, if you
need that. But i need to get inside the lens. Without doing damage. And
without the diaphragm assembly falling out in many pieces.

>    If a cemented component looks hazy after cleaning both
> surfaces its probably the cement. Both Canada Balsam and
> synthetic cements can get hazy although its more common for
> synthetic cement to look this way. Shining a flashlight into
> the lens will often reveal what the cause of the haze is.

There's a "deposit", shaped like an "imprint" of the diaphragm blades, on
the rear group. My guess is that is is grease from the blades that somehow
got onto the lens surface. It must be (at least, i like to think so)
something "constructual", since both my Opton-Tessars show the same thing.
I don't think there is any separation in the rear group. Though the elements
do all indeed look a bit hazy. But that may be a thin layer of grime and
dust (or so i hope ;-)).



End of Rollei Users list digest V12 #63