[filmscanners] RE: scanner dmax discussion

["Chuck Cole" <cncole@earthlink.net>]

> -----Original Message-----
> From: filmscanners_owner@halftone.co.uk
> [mailto:filmscanners_owner@halftone.co.uk]On Behalf Of Clark Guy
> Sent: Wednesday, July 16, 2003 3:28 PM
> To: cncole@earthlink.net
> Subject: [filmscanners] RE: scanner dmax discussion
>
>
> HI, Paul!
>
> I agree that 9 decades (180 dB) is a WWWWWIIIIIIIDDDDDDDDEEEEEEEE
> range, but
> maybe possible.

Possible and quite common for silicon PIN or avalanche detectors (and GaAs).
Some special types of silicon arrays can also do that, but the CCD and CID
types cannot go that far because of their on-chip ancillary circuitry.


> 24bit (144dB) A/Ds are commercially available for digital Audio
> for a while,
> so maybe 30bits A/Ds are being worked on in the lab?  One could sacrifice
> speed for quality more easily in scanning than in audio!

Full range A/Ds are just not especially relevant for this kind of signal.
This is not a scanner signal, just a mark about the intrinsic mathematical
linearity of silicon detectors.  Some real-world spooky systems for
reconaissance and precision targeting do this, but use AGC (automatic gain
control) to adjust between
>
> I would expect something on the order of 14 bits  (84dB) or
> better from any
> good scanner.

Why?  Film isn't as good as 10 bits.  The extra is a big waste of time and
space in computers.


> On further reflection, 30 bits (per channel) would be likely to
> be overkill
> for any but the most demanding instrumentation applications.  A good solid
> 16 bits per channel is probably more than enough for my needs!

Certainly more than enough for any films possible.

Regards,

Chuck


----------------------------------------------------------------------------------------
Unsubscribe by mail to listserver@halftone.co.uk, with 'unsubscribe 
filmscanners'
or 'unsubscribe filmscanners_digest' (as appropriate) in the message title or 
body