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      :: Filmscanners
Filmscanners mailing list archive (filmscanners@halftone.co.uk)

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RE: filmscanners: Pixels per inch vs DPI



Here's one I found:

http://www.digitalcameras.com/howTheyWork2.asp

And I quote:

"The CCD is made up of (usually) millions of tiny sensors that record the
amount of light that hits them. The sensors only record the amount of light
that hits them, not the color of the light. For the digital camera to detect
what color is in each pixel, a special method is used. To capture color, the
digital camera applies a color filter over the individual sensors, the
filter is usually applied directly to the CCD using dye. The most common
filter used is the Bayer filter, see the table at the bottom of this page
for an example. This image would be 4 pixels square on the CCD, a 2x2 pixel
pattern repeating thousands of times consisting of Red, Blue, and Green
filters, and as you may have noticed there are twice as many green squares
as red and blue. This is because human eyes have a sensitivity to the
luminescence properties of green, because it is in the middle of the
spectrum.

*****So a 1 megapixel camera will have 540,000 green pixels, 270,000 red
pixels, and 270,000 blue pixels.*****"

You can do a search for "Bayer and RGBG" and probably find many more
sources...

> -----Original Message-----
> From: owner-filmscanners@halftone.co.uk
> [mailto:owner-filmscanners@halftone.co.uk]On Behalf Of Julian Robinson
> Sent: Monday, October 29, 2001 8:40 PM
> To: filmscanners@halftone.co.uk
> Subject: RE: filmscanners: Pixels per inch vs DPI
>
>
> Austin - is this true?  Can you show documentation to
> demonstrate? - bec if
> it is true then I am very surprised and have been very badly mislead.
>
> Julian
>
> At 10:42 30/10/01, Austin wrote:
> >Note, when a digital camera claims 6M pixels...that's in fact a flat out
> >lie.  It is REALLY 1.5M pixels, with four sensors per pixel...a pixel IS
> >made up of all three RGB components, so it is really misleading
> to make the
> >claims they do.  They would be more honest to call it a 6M SENSOR array.
> >How they get 6M pixel OUTPUT is interpolation...which, of
> course, means that
> >%75 of the image data is just made up, and not real image data
> (to a large
> >degree).  And you thought the scanner dynamic range issue was
> misleading...
>




 




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