Some comments re Phillips 24x35 ccd.
I guess that the fact the sensitive surface is about 2.5 mm
behind the surface of the package is what makes
interchangeable digital backs difficult. Probably not a
problem with an in lens shutter because the sensor could be
recessed into the camera, but a focal plane shutter would
not allow that. This maybe why you can get digital backs for
some medium format cameras but not for 35 mm SLRs.
Shutter: As far as I know ccds do not need a mechanical
shutter. The have an electronic shutter feature, at least
the Phillips ccd in question does. But then, you are not
using the same interface for the ccd as for film.
The Phillips site says you can get ccds up to the 6 inch
diameter of a wafer. That translates to up to 4x5 inches.
Anyone for a 4x5 slide in back?
--Tom
Collin Brendemuehl wrote:
>
> My concerns deal with compensation for the
> mechanical shutter and problems related to it.
>
> Here's some issues:
> #1 -- One roadblock that I faced was dealing with auto-exposure
> mechanisms and curtain travel at higher shutter speeds (you end up with a
> slit).
> How are you dealing with this problem? My net result was that automation
> would be
> lost because of the lack of high shutter speeds controlled by the body.
>
> #2 -- Back availability. To make an interchangable back one must order a
> bunch
> of parts from the manufacturer so that the units can be retrofitted in a
> reasonable
> amount of time. I wouldn't want to lose film usage. And if a mistake is
> made in
> modifying a back, one should have extras available.
>
> #3 -- Interchangability. To add a dark slide isn't a really big mechanical
> problem.
> But it is a cost concern. The slide is needed to protect the sensor when
> off the body.
> Add another $50USD to the price of the unit. And also limit the # of
> bodies that you
> can afford to build them for.
>
> #4 -- Sensor mounting. Because there's some rather convenient rails for
> discerning
> the film plane in every 35mm body, it's easy to build a set of standards
> for the sensor
> to ride on to maintain depth registration. One will simply need to
> engineer a set of
> standards so that it's a simplemechanism on any particular camera
> body. What remains
> is lateral motion. This will happen because of the needed motion to allow for
> interchangability.
>
> If you can resolve these in a cost-effective manner, go for it.
> The circuit isn't much of a problem -- CCDs are almost OTS as far as
> interfacing. And as was stated, go for a 4-AA NiMH system with the IBM
> MicroDrive 1G. You'll have a nice market.
>
> Also, I do C & Assembler programming, esp. with microcontrollers.
> Let me know if you need assistance.
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