On Wed, 21 Apr 2004, Jochen Kunz wrote:
> On Wed, 21 Apr 2004 00:03:36 +0100 (BST)
> ard_at_p850ug1.demon.co.uk (Tony Duell) wrote:
>
> > > Moreover, 3.1M pixels in the camera aren't 3.1M pixels in the final
> > > image. It depends how they're used, but in the camera, you
> > > typically need three pixels, one for each of R, G, and B, to get one
> > > RGB pixel in the image. Some techniques use even more (the Bayer
> > > algorithm uses 4).
> > Argh!. You mean they fiddle the figures? I'd assumed that a 'pixel'
> > was an RGB triad, not a third of one. So you mean you may only get 1
> > million points in the image from a 3.1M pixel camera?
> Yes. E.g. with Bayer you have four sub-pixel per color pixel:
> R G
> G B
> So you get 640 x 480 = ca. 0.3 M "true" color pixels with a 1280 x 960
> "Mega pixel" sesor. The image processing firmware of the camera
> interpolates this later to 1280 x 960 RGB pixels.
> --
<rant>
And this interpolation is very apparent when you try to take pictures of
things like PC cards with fine pitch ASICs. Anything with a high spacial
frequency and multiple colors is royally screwed. Digital camera manufacturers
(and scanner Manufacturers) have gotten away with this deception for quite a
while.
There is no reason tha cameras or scanners should be rated any differently
than LCD monitors (where 1024x768 is really 1024x768 triples)
</rant>
>
>
> tschüß,
> Jochen
>
> Homepage: http://www.unixag-kl.fh-kl.de/~jkunz/
>
>
Peter Wallace
Received on Wed Apr 21 2004 - 10:43:22 BST