[rollei_list] Re: Ground-glass image on 3.5 Tessar vs. 3.5F Planar
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <rollei_list@xxxxxxxxxxxxx>
- Date: Wed, 2 Feb 2011 13:26:38 -0800
----- Original Message -----
From: "Adam Gori" <adamgori@xxxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Wednesday, February 02, 2011 12:06 PM
Subject: [rollei_list] Re: Ground-glass image on 3.5 Tessar
vs. 3.5F Planar
Thanks, Marc. It might be as simple as that. I haven't
looked at the mirror.
The viewing glass is pretty much pristine, so it's not
that.
Look back through the finder lens. You will see if the
mirror is damaged or the lens is hazy. Both can be fixed
although cleaning the insides of the finder lens is not
trivial because the front panel of the camera must be
removed to get the lens apart.
The mirror can be cleaned by removing the finder hood
(four small screws). Before cleaning blow the surface of the
mirror off with canned air or a hand air bulb.
It should be cleaned with pure Isopropyl alcohol on a
lintless tissue or cloth. saturate the tissue and fold it,
lay it on the surface of the mirror and drag it off. If
there is still something on the surface use a fresh tissue
and repeat. Use each tissue only once and discard it. This
will remove haze and dirt without leaving streaks.
The screws on the camera has finer slots than normal
screws of the same size. If a standard jeweler's screwdriver
is used it will damage the slots. Take a cheap jeweler's
screwdriver and grind down the tip using a wet stone until
it fits. Similar narrow slot screws are used in other
machinery, typewriters for instance.
The back of the finder lens can be cleaned when the
finder hood is off. However, these lenses tend to get hazy
inside which substantially reduced contrast and
transmission.
If the finder lens is dirty inside you may want to send
the camera to a good camera technician. If you want to
undertake the job yourself you must remove the front cover
from the camera. You can probably open the finder lens
without removing it from the camera. Most of these lenses
have a tiny set screw in the side. When loosened the outer
part of the mount can be unscrewed. The mount has a front
element, a spacer, a center element, another spacer, and the
rear element inside. Make a careful drawing of the spacers
so you can get them back in correctly. The center element is
_nearly_ biconcave so its hard to see which way it goes.
However, one edge is chamfered so note which way it points.
If the center element is reversed the image quality will be
awful. Also, note the orientation of both end elements. Both
are bi-convex but again not symmetrical and direction
counts.
The lens barrel is locked in place by a set screw (some
cameras have a clamp arrangement). If you must remove the
lens you will have to re-establish co-incidence of focus
with the taking lens. That requires a test ground glass for
film gate. Since you have a Maxwell screen, which often
employs shims you can get rid of them and refocus correctly
at this point.
The surfaces can be cleaned with any lens or window
cleaner or alcohol. The difference made by even a small
amount of haze is astonishing.
--
Richard Knoppow
Los Angeles
WB6KBL
dickburk@xxxxxxxxxxxxx
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