[filmscanners] RE: Repeated "Tonal correction", is it god?

["LAURIE SOLOMON" <laurie@advancenet.net>]

To put words in shAF's mouth (hope you don't mind shAF), the use of a
greater bit depth - 16 bits/channel rather than 8 bits/per channel - allows
one to capture a much more expansive tonal range rather than the more
compressed range of an 8 bit per channel capture.  This means you will have
more tonal detail and subtlties available within the range and captured by
the data.  Thus, with a 16 bit scan, you have more tonal inforamtion to deal
or play with; but once you reduce the tonal range by converting to an 8 bit
file or once you have performed your first tonal adjustment, you have thrown
away some of that original data or altered it in a manor that it cannot be
recaptured by new adjustments or even in many cases reconstructed so as to
be exaclty as it originally was.  Thus all secondary corrections can be
working with artifical information interpolated from the previously altered
data and can produce noise and artifacts rather than an actual real
representation of what the real data would have been prior to the first
alteration.

Hope this helps.  I will leave it to shAF to both correct me or make my
explanation clearer and more articulate.
-----Original Message-----
From: filmscanners_owner@halftone.co.uk
[mailto:filmscanners_owner@halftone.co.uk]On Behalf Of Nagaraj, Ramesh
Sent: Thursday, March 13, 2003 1:59 PM
To: laurie@advancenet.net
Subject: [filmscanners] RE: Repeated "Tonal correction", is it god?





shAf writes ...


> No ... the reason is why you scanned into 16bits.

>  Again no ... assuming 16bits again.  If 8bit channels, then yes, you'd
>want to get all tonal adjustments correct (as possible) with the scan
>software.  However, I doubt anyone will notice a minor post-scan adj't with
>PS.

I am not able to clearly understand how that is related  to bits/channel.
Could you please explain this?

Are you implying the following..
Because there is no extra to data to play with in case of 8bit/channel, its
good to do pre-scanning correction.
In case of 16bit/channel, there will be more data, so we can afford to waste
data during post-scan correction; thus no need to do pre-scan adjustments.

Thanks
Ramesh



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