In article , Jim Brokaw <jbrokaw@xxxxxxxxxxx> writes
Seems like the OM's that are data-back capable would be able to work with a
rudimentary interface with an intelligently-designed digital back.
The pressure plate occupies roughly the plane that the image sensor needs to
fall in. The OM's are manual focus, would need to be manual exposure
setting, or operated in that mode. The critical need would be for the
digital back electronics to 'read' the image sensor at the right instant
after the shutter is open. This could probably be triggered from the x-sync
signal.
You'd have to set the shutter at 1/60 for a full image-sensor illumination
at once. I suppose you could incorporate higher shutter speeds
electronically in the digital back, with a setting separate from the camera
setting... but manual exposure only. Once the image sensor is scanned, the
digital back could write the data to a storage device, and reset on its own.
Image processing software could compensate for the lesser illumination of
our non-digital spec Zuikos to get an even image despite those nasty
off-axis light rays. You'd still have to wind the shutter to reset the
camera body.
I don't see how any of this is unfeasible, but to have it make 'business
sense' might be difficult given the current cost of full-frame image
sensors. I suppose you could use a smaller sensor, but then why not just use
a digital camera... I suspect that in a few years the cost of 24mm x 36mm
images sensors will drop to a point where they can be played around with. We
already did a soldering iron survey, I'm ready...
I looked into doing this for personal use a couple of years back with a
Philips FT-3020C 24x36mm CCD and a modified OM-1n and its not as easy as
you suggest at all. The first mistake you have made is in the first
sentence of the second paragraph - the image plane is the milled
surfaces that the film is held against by the pressure plate, not the
plate itself. Since the CCD is encased in a ceramic package with a
window (typically 2-3mm physical distance beneath the surface of the
window - less optically because of the refractive index of the window
itself) you need to mount the CCD package further forward than this.
That requires some serious metalwork on the OM body, but even then the
dimensions are such that the package would foul the shutter curtain and
prevent its operation. There is insufficient focus adjustment on the OM
cameras to permit shifting the focal plane to permit the CCD package
just to align on the film runners. :-(
Also, the databack contact isn't really suitable for synchronising. The
best solution is to use the mirror-up switch contacts on the base of the
camera - you will need to use space on the base in any case to build a
unit with enough power and storage capacity for your images in any case,
so this isn't as inconvenient as you might think. The CCD can then
easily be synchronised for exposure at all speeds. The mirror-up
contacts just take the device out of reset (start of integration), the
shutter exposes the CCD, the mirror contacts confirm exposure is
complete and initiate the readout sequence. Using appropriate circuits
a second frame of the same integration time can then be taken with the
shutter closed to correct for dark current. Ideally a secondary shutter
release similar to that used on the motor drive/winder mechanism would
prevent operation faster than the time required to readout the CCD
twice.
The only problem I couldn't overcome was getting the CCD to the film
plane itself - and I certainly wouldn't recommend taking the CCD out of
the package. Even if you did, there is still the issue of getting
electrical contact to it without shorting onto the camera body. I guess
it could be done, but it would require significant metalworking around
the shutter - which would necessitate a complete disassembly of the
body. That was more than I was willing to take on for a personal toy at
the time.
Incidentally, I noted the comments Olympus made on the suitability of
the OM optics for digital cameras and my primary reaction was
"Baloney!". I have actually built a camera (well two actually) with an
18mm f/3.5 Zuiko fitted to a colour CCD and there were no discernable
colour problems at all. Now this may not be the widest lens in the OM
group, but it's close. My reason for using the short focal length was
because the application was for a free-swimming underwater submersible
for oil pipe inspection. This required stereo vision (hence the two
cameras) and, being underwater, the effective focal length was
multiplied by 1.5, roughly the refractive index of sea water - so it
functioned more like a 28mm f/2.8. Now I have to admit that the
chromatic impurity issue did concern me before I did this, but since the
problem didn't arise with that lens, I find it hard to believe that it
would with any other lenses in the OM range. My conclusion is that
Olympus are just not interested in maintaining compatibility with legacy
products when they can sell everyone new lenses. Any story that
suppresses the demand for such compatibility is worth peddling.
--
Kennedy
Yes, Socrates himself is particularly missed;
A lovely little thinker, but a bugger when he's pissed.
Python Philosophers
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