Canon comes out with yet another camera - this one is a real 'prosumer'
version using the EOS 30/Elan 7 body and functions...
On the 'mechanical shutter' issue, This is from the DP Review site
They are different types of noise. Random noise, which is what we
> are all used to seeing, won't increase with the exposure length.
> The problem is that semiconductors are never fabricated perfectly
> and each photosite will be a little different than its neighbour.
> As such, each site typically has a small current that adds to the
> accumulated charge as one integrates (exposes).
>
> With a short exposure, this current is so small that it really
> doesn't effect the image all that much. However, over a long
> exposure that current can add up and get to a point where it
> becomes visible and hurts the image. The upside, however, is that
> this noise is predictable and can be completely removed via a
> process of dark frame subtraction. That is, you take the image,
> then you close the shutter and capture the image of the dark
> shutter blades for the same time and in the same temperature (dark
> current is dependant on the ambient temperature). The second image
> contains only the noise, so it can be subtracted from the first
> image and all the dark noise goes away. This is what the 760
> currently does, and is likely what Kodak will add to the 14n at a
> later time. You can also do this manually on any camera using
> Photoshop or a similar package.
>
> Some of Canon's cameras (I believe the D60 has it and the 1Ds might
> as well) have logic at the photosites to measure this dark current
> and remove it without the assistance of the second exposure. This
> saves the trouble (as the dark frame subtraction would require a
> minute for a 30s exposure) however it also eats up some of the
> photosite space.
----- Original Message -----
From: <focus@adnc.com>
To: <karlsch@earthlink.net>
Sent: Tuesday, February 25, 2003 9:29 AM
Subject: [filmscanners] Re: Canon IDs vs Pentax 67II
Again, it's worth noting that the E-20 can work in both modes, but only
gives half the
resolution in the "software shutter" mode. There must be something about
"software shutter"
operation that limits/impairs resolution.
Karl Schulmeisters wrote:
> My understanding of the physics of the imagers is that you get much better
> performance if you keep the imager dark until you take the image. So the
> image quality does depend on the shutter. And by keeping the imager dark,
> you don't have to reset it prior to capturing the image so you minimize
> shutter lag.
> ----- Original Message -----
> From: "Austin Franklin" <austin@darkroom.com>
> To: <karlsch@earthlink.net>
> Sent: Sunday, February 09, 2003 12:07 PM
> Subject: [filmscanners] RE: Canon IDs vs Pentax 67II
>
> Hi Karl,
>
> > for SLR digicams, there is a real shutter.
>
> It has to do with the sensor type, and interline sensors, that the cheapo
> digicams use have an electronic shutter.
>
> > That's in part why
> > they have so
> > much better image quality
>
> They have better image quality because the sensors are so much better, not
> because they use a shutter!
>
> > and less shutter lag than consumer
> > digicams.
>
> I don't believe that has anything to do with the shutter, I believe it's
the
> sensor and camera design, shutter or not.
>
> > I can elaborate on why later.
>
> Please do ;-)
>
> Regards,
>
> Austin
>
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