[pure-silver] Re: old rollei over exposing
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Fri, 18 Feb 2005 12:29:06 -0800
----- Original Message -----
From: "Jim Brick" <jim@xxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Friday, February 18, 2005 9:23 AM
Subject: [pure-silver] Re: old rollei over exposing
> At 10:59 PM 2/17/2005, Michael Healy wrote:
>
>>Okay, WHAT manufucturers generally recommend? Point us to
>>a source or three. Show us they recommend leaving it
>>cocked, or show us they
>>recommend NOT leaving it cocked.
>
>
> OK... take Hasselblad for instance. It is not that they
> tell you one way or
> the other, they simply do not provide you with a way of
> uncocking a lens
> shutter. The ONLY way to mount or unmount a lens from a
> Hasselblad is, if
> the shutter is cocked. Hasselblad provides no way of
> uncocking a shutter
> when it is off of the camera. Yes, you can do it, but
> Hasselblad tells you
> that if you should accidentally uncock a lens shutter
> while the lens is off
> of the camera, you should cock it again using a coin and
> provided coin
> slot. Even focal plane shuttered Hasselblads (I have two)
> operate this way
> as they can use shuttered and non-shuttered lenses. The
> focal plane
> shutters as well as the lens shutters, stay cocked.
>
> ALL stored Hasselblad shutters, whether in original boxes
> awaiting sales or
> in a photographers bag, or in great grandfathers closet
> awaiting the
> eventual grandson finding it... are cocked.
>
> You simply do not have uncocked Hasselblad shutters laying
> around. After
> exposing a frame, you ALWAYS wind the camera which cocks
> the shutter and
> advances the film. Not doing this can be a problem. a.)
> you cannot remove
> the lens in order to use another, and b.) If you change
> backs, you risk a
> double exposure on the removed back and a skipped exposure
> on the new back.
>
> The first Compur shuttered Hasselblad 500c appeared in
> 1957. Hasselblad
> lens shutters, from that day on, have remained in the
> cocked state as the
> norm. Yes, some ne'er-do-wells have, undoubtedly, using a
> toothpick,
> tripped all of their Hasselblad lens shutters thinking
> they were doing
> their shutters a favor. Based upon the way the system was
> designed, I
> believe they were not.
>
> IMHO,
>
> :-)
>
> Jim
>
BTW, the type of spring used in the old "dial set" Compur
is similar to that used in the latest (as used on Hassy and
Rollei) version. That is both use a flat spiral spring like
a clock motor. These are always partially tensioned. Later
Compurs, of the "rim set" variety, up to the EVS shutters,
used coil springs. Actually, these are also partially
tensioned all the time. The idea probably is to minimise the
difference in available drive force as the shutter is
operated.
Middle age Compurs of the Compur Rapid type have an
additional booster spring for the highest speed. This is
compressed by the speed dial and accounts for the long
travel between the next to highest speed and the highest
speed and for the force needed to get there. Its probably a
good idea not to leave this spring tensioned all the time
although it may not make any difference. The reason these
shutters should not be put into the highest speed position
(usually 1/400th or 1/500th) is that the force needed to
compress this spring while the shutter is cocked may force
it under the speed ring jamming the shutter. It could also
wear the ring and spring if done often.
Its probably OK to go from the highest speed to a lower
one.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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