In a normal digital camera with a single CCD, each of the state pixels (3.3,
4 MP, whatever) captures only a single color. A typical arrangement thus
is:
Row 1: GRGRGRGRG...
Row 2: BGBGBGBGB...
Row 3: GRGRGRGRG...
Row 4: BGBGBGBGB...
and so on.
In order to fulfill the need for a 3 color component for each "pixel" in the
final image, neighboring sensor color values are combined (there are various
algorithms to do this) to form a 3 color pixel. No, in order for this to
not produce digital artifacts such as color fringing of high contrast edges,
the image on the CCD is slightly anti-aliased, by either or both methods of
slightly defocusing the image, or in software later.
The end result is that there is a loss of detail.
Scanners on the other hand, have 3 rows of sensors:
Row 1: GGGGGG.....
Row 2: BBBBBB.....
Row 3: RRRRRR.....
With this, the G row is exposed, and then a micro step is done (either the
CCD or the film/print), and the B is exposed for the same position on the
image, and then microstepped again to expose the R row. In practice, all 3
are exposed simultaneously, but for different rows of pixels on the image,
thereby pipelining the operation such that 3 rows of pixels are getting
another color added before the CCD moves along the image to the next pixel
row.
Fuji has an odd arrangement of hexagonal array CCD sensor elements, and
actually produce more fictitious image pixels, and claim a picture pixel
output higher than the CCD sensor count itself (while each CCD sensor is
still a single color).
Hope this helps.
Gerald
----- Original Message -----
From: "Alexandre A. P. Suaide" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Wednesday, June 06, 2001 2:24 PM
Subject: Re: Digital: The next level
> Let me understand.... If one digital camera (say Nikon coolpix 990)
> produces images with 2048 x 1536 pixels it corresponds to something
> about 3 megapixels, right? So, If what you are saying is correct,
> the CCD sensor of this camera has about 9 megapixels, because each of
> the pixels is obtained from a red, green and blue component (you
> are saying that each pixel is one color and the final pixel is the
> mix of three sensor pixels). In your affirmative, a 3 megapixel camera
> gives in the end only a one megapixel resolution, right?
>
> Alex
>
> Michael Nosal wrote:
> >
> > At 12:35 PM 6/6/01 -0700, you wrote:
> > >It still only produces a 4 mega pixel image from 12 mega sensors.
> > >
> >
> > Yes, but with it each channel gets a full 4 megapixel's worth of info.
Other
> > sensors may have 4 mega pixels, but 1/3 are red, 1/3 are green, 1/3 are
blue
> > (often the ratio isn't 33% for each color, as the sensitivity of some
> > channels is greater than others.)
> >
> > This will produce a way better image than a single 4mp sensor.
> >
> > Michael Nosal
> > [EMAIL PROTECTED]
> >
> > -
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>
> --
> -----------------------------------------------------------------------
> Alexandre A. P. Suaide, Ph.D. mailto:[EMAIL PROTECTED]
> Physics Department
> University of Sao Paulo - Brazil Phone: 1-313-577-5419
> Wayne State University - MI -USA ICQ number: 78139605
> -----------------------------------------------------------------------
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