I don't think the camera shutter would be used except to protect the
CCD. The only way for a camera to tel the CCD to turn on and capture an
image without a custom connection to the camera is through the flash
sync connection. Only X-sync is available on recent cameras, and it
fires after the shutter is open, and on many cameras, including later
OMs, doesn't fire at all above 1/60. Thre is no other way for the CCD to
know when the shutter is fully open. Sensing the advent of light as the
shutter starts opening seems tricky because of shutter travel variance
with brand, model and individual body. The flash sync can at least be
relied on to be accurate on a properly functioning camera, or the flash
wouldn't cover the whole frame.
I think the SFilm would take it's cue from the X-sync that the shutter
is fully open, so it should capture and store an image. the 'shutter' on
digital cameras isn't mechanical anyway, but a function of the CCD
driver firmware. The host camera would be set at a shutter speed that
assured the second curtain didn't release until the longest CCD exposure
allowed was conplete. Making exposures over about 1/2 second might
require the camera on B and holding the release until a beep is heard,
or some such. Any body that accepts a date back without a sync cord has
a sync signal readily available at the back.
Likewise, TTL exposure info from the camera meter isn't available to the
CCD. TTL exposure would be the only option and a function of the CCD
firmware. The Camera meter would work like the OM-2(n), providing an
estimate of the actual exposure to be carried out by a conpletely
different system. Hey, that gets difficult if you are trying to see what
shutter speed to anticipate, but have to actually shoot at a slow speed.
Designing a thing like this to drop into legacy cameras, without
modification of the camera, is not at all easy. That's probably why they
went the replacement back & bottom module route the second time. Still
tricky coordinating CCD shutter speed and viewfinder meter display, esp.
for more than 1-2 body designs. Not sure I can see how.
Moose
Chuck Norcutt wrote:
In all the discussion of the probability and/or suitability of a
digital back for our OM's no one has yet mentioned the problem of OTF
light measurement for auto exposure control. I don't know what the
roll-over point is between measuring off-the-curtain and off-the-film
but I'm pretty sure we're there by 1/60th of a second. So, unless the
silicon surface just happens to be pretty close to film in
reflectivity there would be exposure error for most slow speeds
including all auto flash work.
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