Re: [APML]: Lens quality

["Tom Krajci" <krajcit@det5wg57.barksdale.af.mil>]

> From:          Chuck Vaughn <aa6g@aa6g.org>

> > When the CCD doesn't get much light to detect, then the noise
> > contribution from the CCD is significant.
> 
> Undoubtedly....but that brings up a question and I don't know if anyone
> has an answer for it. Are the CCDs in a scanner being used down to their
> minimum sensitivity? The manufacturers must be aware of noise a low signal
> levels. Maybe they don't use the chip below a certain signal level. Maybe
> less expensive scanners use a less expensive chip with a smaller dynamic
> range and they use more of that dynamic range and therefore produce noisier
> images with dense negatives.

That's an excellent point!  I don't have any spec sheets to help 
answer that, and I haven't done any scan tests in this area either.  
But I still have problems scanning faint nebulosity on 
slides/positives.

Until I can figure out better techniques I'm gonna live by these 
rules.

1.  No matter what you scan, get as much light as possible, just 
short of saturation, to the scanner.

2.  If I'm going after faint fuzzies I'll scan negatives.  If I'm 
going after bright stuff slides are preferred.

Any suggestions on how I can improve what I'm doing?  (Yeah, buy a 
$10,000 scanner!  ;-)

Thanks,
Tom Krajci

Capt Tom Krajci
B-52 Intelligence Officer
"Intelligence:  Ignored in peacetime, blamed in war!"
http://spur.barksdale.af.mil