on 4/25/02 1:22 AM, T.Clausen@xxxxxxxxxxxx at T.Clausen@xxxxxxxxxxxx wrote:
snipped a bit...
> I actually think that building a camera with a large number of electronic
> circuits is *easier* and *cheaper* than building a mechanical camera such
> as the OM1 and OM3Ti. E.g. I would probably be able to fairly easilly
> device a precise high-speed electronic shutter (at least the timing
> circuitry etc), whereas the thought of making a mechanical shutter really
> scares me. Also, electronic transmission of apeture and shutter settings
> to the meter has to be easier to make and maintain (just an electrical
> wire that never moves) than having mechanical transmission (in OM's this
> is transmitted through a string that moves and pulls various levers,
> right?)
You really don't need to design the shutter, just use the available design
i.e. Copal. They are all modules, probably with variations for major
customers preferences.
The key issue in making a 'third-party body' viable is coupling the various
manufacturer's lenses. What you need is a kind of 'reverse Adaptall 2' where
the interface to the camera is your own design and the interface to the lens
is the lens manufacturer's design. The problem is that many of the manual
focus lenses use various levers and pins to transmit lens aperture
information and trigger aperture shutdown, and the levers and pins are in
different locations around the mount... and some move radially and some move
back and forth. If you don't need auto aperture and coupled (full-aperture)
metering the design is much simplified.
Electronic designs such as Canon EF mount are easier mechanically, because
the mechanical coupling is just the bayonet mount, easily
reverse-engineered. The electronics are more complex because you would no
doubt be doing the reverse engineering without the aid of the manufacturer,
and this has proved to be a problem for third-party lens makers. I have a
Sigma zoom for Canon EF that did not work on the Canon EOS Rebel that I
tried it out on... that's probably why it was $10 in a thrift shop. When I
got my Canon EOS IX I tried the same lens and it works and focuses perfectly
(a lot noisier and slower than the Canon USM lenses...) There must be some
incompatability between the lens electronics and the EOS Rebel body
electronics. So even Sigma, which has a lot of engineering resources, has
had trouble getting the electronics right (I think Canon changes proprietary
details to achieve this intentionally).
If you design a rangefinder/viewfinder camera, the problem becomes coupling
the focus to the lens, I suppose some kind of electronic focus sensor could
be used to relay an 'in focus' signal to the viewfinder, like the OM-F only
with a rangefinder... even without the mirror you still have the backfocus,
so the rangefinder wouldn't be much smaller than the SLR design. You could
design your mount to stop the lens down all the time, and use a meter
readout which functions like the stop-down metering of old SLR's, which
would be simpler. At least a rangefinder/viewfinder camera would avoid
needing a mirror mechanism, and could be quieter. Even allowing for back
focus it might be smaller also.
--
Jim Brokaw
OM-1's, -2's, -4's, (no -3's yet) and no OM-oney...
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