[rollei_list] Re: OT: Question re shutter CLA and Ronsonol
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <rollei_list@xxxxxxxxxxxxx>
- Date: Wed, 12 Jan 2005 16:43:52 -0800
----- Original Message -----
From: "Ardeshir Mehta" <ardeshir@xxxxxxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Wednesday, January 12, 2005 10:20 AM
Subject: [rollei_list] Re: OT: Question re shutter CLA and
Ronsonol
>
> Still, at one time I did try to unscrew the front elements
> of the
> Tessar lens to try and get to the shutter in order to
> clean it. I did
> manage to unscrew the front element using a rubber stopper
> (I don't
> have a lens wrench) but the shutter is apparently behind
> TWO lens
> elements, and I couldn't unscrew the second element. So I
> just put the
> front element back.
>
> I am wondering about the slot in the left bottom side of
> the lens, and
> why this camera has it. Maybe you can enlighten me. A
> little lever
> protrudes therefrom, which can also trip the shutter. The
> camera is an
> early model Automat. Through this slot some bits of the
> shutter
> mechanism are actually visible. I can squirt vast amounts
> of Ronsonol
> into the shutter though this slot. I can also drain
> dissolved stuff
> out, and at one time quite a bit of sludge came out though
> it after the
> Ronsonol had loosened it up. Bits of black solids also
> came out -
> specks of stuff like maybe tiny paint chips? I thought I
> was succeeding
> in cleaning the shutter off completely, in fact - so much
> stuff came
> out. But apparently I was wrong, for after the Ronsonol
> evaporates the
> shutter still sticks, though not nearly as much as it used
> to.
>
> But the question remains in the back of my mind: what
> happens after the
> CLA? Won't dust and dirt get into the shutter again,
> through this slot?
> My 2.8D doesn't have such a slot, and its shutter seems to
> be totally
> sealed against the elements. Why, then, does this one have
> such a slot,
> though which dirt can get it? I am mystified.
>
> Cheers.
You managed to get the front element off the lens without
removing the front cell. Its useful to be able to do this
because it allows cleaning the surfaces inside the cell but
it is not something that needs to be done more than once in
twenty years.
Compur shutters are constructed so that the mechanism is
not exposed when the lens cells are removed. In order to get
to the works one must remove the front cell and take off the
front cover of the shutter. That allows removal of the speed
ring. Once that is off its possible to remove the retarder
mechanism. That is the worst offender in a shutter which is
behaving irregularly. The regulator is a clock-work
mechanism. Its cleaned by soaking it in Naptha followed by
pure alcohol. Once cleaned its lubricated by putting the
tiniest amount of fine oil on the trunions of the gears and,
perhaps, a touch on the pallet. Suitable oil is available as
Nyoil and the finest grade of Lebell silicon oil, available
at hobby shops. The retarder is replaced and its position
shifted until 1/10th second is exactly correct. The other
speeds should then be accurate.
Further cleaning really requires removal of the entire
shutter from the camera and its disassembly. Its important
to have a drawing of the thing so you can see how to get it
back together. The shutter and diaphragm blades are cleaned
in solvent and the shutter blades polished to remove any
trace of residue. The shutter is then re-assembled. Some
Compur instructions indicate that a trace of light grease
should be used in a couple of places but I was told by a
fellow at Compur several years ago to just leave it dry.
The top speed of Compur and most other shutters is the
_effective_ speed for the full shutter aperture. Since the
shutter has a finite opening and closing time this is rather
faster than the total open time as measured for a small stop
or by a small sensor at the center of the aperture. For
Compur-Rapid and Synchro-Compur shutters the marked top
speed is about 80% of the total opentime. i.e., for a
shutter marked 1/500th second the measured top speed is only
about 1/400th. I think Compur specifies somthing like
1/380th as the limit. Compurs should be within about +/- 5%
for speeds to the top speed but that one can vary as much as
20% from the nominal speed.
The use of effective speed markings is also found in
focal plane shutters, particularly Speed Graphic and Graflex
cameras because the shutters in them are not very efficient.
It is possible to measure the _effective_ speed of either
a leaf or FP shutter using the little Calumet tester but it
requires careful set up so that the light intensity at the
half open and half closed points fall at the threashold of
the sensor.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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