EU

[Jim Battle]

Chris M wrote:
> now an even better idea then a scanner is a digital
> camera. 2 - 3 megapixels (even 1.2!) is sufficient for
> archiving text and graphics. It MUST have the ability
> where you can vary the focal length (able to move a
> fixed focus lense in and out in relation to the image
> sensor. And you thought I wasnt going to say that all
> wrong?). I would also deem ancillary storage (i.e
> cflash etc) a necessity. Cheaper to ship then a
> scanner. Flat bed scanners are unwieldy, especially
> when it comes to archiving bound stuph.

What you propose is something to do if you are desperate, but not 
something you'd want to do routinely.

Taking a picture of an 8.5" x 11" sheet of paper with a 1.2 mpix camera 
would get you 113 DPI.

In reality, it is worse than that.  99% of all digital cameras lie about 
their DPI -- a 1.2 mpix camera doesn't have 1.2 mpix red, 1.2m green, 
1.2m blue sensors.  Different sensors have different patterns, but 
essentially they count each r, g, or b subsample as a pixel and 
interpolate.  a common pattern is a tiling like this

     R  G  B  G
     G  B  G  R

Heavy duty image processing does its darnedest to hide this fact, but it 
is obvious in certain circumstances.  Take a picture of a B&W newspaper 
from some distance where you will get some aliasing and then look at the 
picture -- you'll get lots of color fringing.  The only camera sensor 
that doesn't do this is the one from foveon:

     http://www.foveon.com/

This is a nice tie in to classiccmp -- the CEO of Foveon is Federico 
Faggin, co designer of the 8080 and co-founder of Zilog.

Finally, the linearity of cameras is horrible for work like this, so the 
effective DPI will drop even lower.