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



- ----- Original Message ----- 
From: "Q.G. de Bakker" <qnu  
To: <rollei  
Sent: Thursday, May 01, 2003 6:08 PM
Subject: 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.
>
  Its possible it lifts out. A safe way to lift it is with
Scotch tape. It won't scratch the surface and grips enough
to remove elements.
  If it comes out be careful to note any spacers associated
with whatever comes out.
  If you can get the entire rear cell out, and this is a
Tessar, there should be only the one lens in it, i.e. the
cemented pair.
  AFAIK (Marc?) Zeiss did not make any leneses other than
conventional Tessars under that name. They certainly made
modified Tessar type lenses, but with other names, such as
Biotessar.
- ---
Richard Knoppow
Los Angeles, CA, USA
dickburk  

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