DrT (George Themelis) wrote:
Ah, I see you found the list without my help. :-) Welcome!
>> Most manufacturers had a different winder or drive for each camera model,
>> but all of olympus's winders/motors work on all bodies!
>>
Not quite true, although the exceptions are few, OM-707, OM-101 and OM-2000.
>
> Yes, it is clever. Someone might claim that it is limited at the same time:
> Cameras with an electrical shutter (OM2, OM4) can be triggered by just making
> an electric contact (sorting two wires).
Not true, I'm afraid. Although the shutters are electronic, the release
mechanism remains mechanical. The button or cable release on the top
plate releases the mirror. As the mirror reaches the top, it activates
either the mechanical or the electronic shutter. One could probably rig
an electronic release of the shutter, but the mirror would still be
down, so no picture.
Thus, the mirror and aperture pre-fire on the OM-4 series can simply
interpose an electronic delay after the mechanical mirror/aperture
activation.
The Winders and motor drives provide the simple, "short two wires"
shooting of OM.
> This is not an option with Olympus. ... The mechanical cable release could
> shake the camera (at least in
> theory, in high magnification or astrophotography applications).
>
Here, you enter one of the dirty secrets of the OM system. To quote from
myself a couple of months ago:
==============================
"A breakthrough camera, sure. Without fault, nah.
The major failings in the camera itself relate to vibration control. The
design of the lens aperture and stop-down mechanism is inherently
flawed. Oly worked around that starting with the OM-2sp, then the 4
series, OMPC and OM2000, but all used the self timer, which isn't
variable length, which is a slow and awkward way to work for many
applications.
OM lenses have the diaphragm held open by a spring in the lens. The
camera has no idea what the actual movement needed for any stop is, so
it simply slams the lens operating pin against the stop inside the lens
in a circular motion. Because the camera body has to operate even very
large diaphragm mechanisms, its action is quite strong. This causes lots
of motion and vibration. Gary's tests* proved conclusively that the
mirror lock-up alone on the OM-1 is simply ineffective at controlling
vibration - possibly why there isn't one on the OM-2(n).
Nikon F lenses are the reverse, with a spring in the lens holding the
aperture closed against the internal stop set by the aperture ring. The
camera operating lever just moves down and up, without a bang at the
end. The bang, a smaller one because of the smaller mass of the parts
involved, happens out in the lens, and is proportional to the operating
force required by each lens. So small, light lenses have a small bang,
big heavy ones a bigger one.
In the case of the F series, the sheer mass of the camera helps minimize
vibration effects. Then of course, the F series has a mechanical MLU AND
aperture pre-stopdown mechanism. "
==============================
Thus, any possible vibration from a mechanical release is nothing. It is
either overwhelmed by the other sources or occurs, along with mirror and
aperture mechanism, before the long settle down delay of a self-timer.
I believe the reasons the OM-1 has been such a popular camera for
astro-photography in spite of the limitation are two. First, the mirror
lock up lever gives the impression of vibration free shutter release.
Second, the actual vibration time is so short relative to the total
exposure that it has no noticeable effect.
Moose
*
http://web.archive.org/web/20070311095348/http://members.aol.com/olympusom/lenstests/default.htm
--
_________________________________________________________________
Options: http://lists.thomasclausen.net/mailman/listinfo/olympus
Archives: http://lists.thomasclausen.net/mailman/private/olympus/
Themed Olympus Photo Exhibition: http://www.tope.nl/
|