Re: umax-backend

Rogier Wolff (R.E.Wolff@BitWizard.nl)
Mon, 1 Sep 1997 08:38:31 +0200 (MET DST)

Jonathan A. Buzzard wrote:
>
> On a the only quality assurance program I have ever seen for a scanner,
> the low couple of bits where just noise (a =A320,000 12bit grayscale scan=
> ner
> for X-Ray films using a stablised HeNe laser and a photomultiplier tube).=

Yes, the q/a program will show "only noise" still, the doctors won't
allow you to trhow away that information. Maybe if you average 4 pixels
together that you get a little information. This IS visible to the
naked eye.....

> I doubt it is any different on a compartitvely cheap UMAX scanner
> with a CCD and flurescent lighting, so just chuck the two low bits
> from each cha= nnel, which are probably noise anyway and treat it as
> a noiseless 24bit scanner= =2E

Things like good 12bit a/d converters are getting cheaper and cheaper.
I wouldn't discard a (still sold as "professional") modern scanner as
junk when you've got a datapoint of a few years ago.

How do you measure the "just noise" in a 12bit scanner? I'd try to
generate a perfect analog greyscale and scan that.

Roger.

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