RE: filmscanners: RE: filmscanners: pushing dynamic range on the nikon 4000ed--What is Analog Gain

["Alex Zabrovsky" <alexz@zoran.co.il>]

BTW, is the amplifier stage always implemented between the CCD analog output
and ADC input ?
Are there scanner's implementations utilizing digital gain (multiplications
after appropriate digital filtering) rather then in analog domain ?

Regards,
Alex Z

-----Original Message-----
From: owner-filmscanners@halftone.co.uk
[mailto:owner-filmscanners@halftone.co.uk]On Behalf Of Austin Franklin
Sent: Monday, November 19, 2001 4:07 PM
To: filmscanners@halftone.co.uk
Subject: RE: filmscanners: RE: filmscanners: pushing dynamic range on
the nikon 4000ed--What is Analog Gain


> Unfortunately this isn't what it actually does.  The "analog
> gain" actually
> changes the integration time ie. how long the CCD is exposed for.
>  The longer
> the exposure, the greater the "analog gain".

Where did you get the idea (as in a source of information) that exposure
time is "analog gain"?  Gain is something entirely different than exposure
time.  Time is, well, time.  Gain is amplification of a signal...though that
does increase over time, I don't believe that qualifies as "analog gain".

In every digital imaging device I've ever designed or worked on, gain has
specifically been the control of the output amplifier between the CCD and
the A/D, and is typically determined by calibration.  It is used to offset
the variance in illumination that can occur over time.