--- Chieh Cheng <[EMAIL PROTECTED]> wrote:
> >
> http://www.dpreview.com/reviews/canond30/page2.asp
> >
> http://www.dpreview.com/reviews/canond30/page7.asp
>
> Now why does a digital camera require a shutter
> curtin for its
> CCD or CMOS sensor?
> Wouldn't it be better to just turn the sensor on and
> off to
> capture the image?
> There would be no mechanical parts and perhaps less
> battery
> drain.
I have asked the same question just a few weeks ago.
Actually, I am not sure if for CMOS you really can
turn the sensor on and off, i.e. stop producing
electrons while the sensor is still exposed to light
and in the same time keep the already collected
charge. In case of a CCD there are other solutions
like IT-CCD, FT-CCD, and IFT-CCD. I think these kind
of CCD are actually used for digital film cameras
where you have no shutter. For these kind of CCDs you
have to give up some area for the protected pixels.
This will reduce sensitivity unless you use a micro
lens. I am not sure what happens with the spatial
resolution. With the micro lenses it probably does not
change. Nevertheless, you give up quite a bit of area
for the protected pixel which you could use for
additional pixels. If high resolution is important
(for digital camera it is but not really for video
cameras) then you probably should not use these kind
of CCD and therefore you need a shutter. Just
guessing.
Robert
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