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

["Austin Franklin" <austin@darkroom.com>]

Hi again, Laurie,

> 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.

That is correct...but...

> This means you
> will have
> more tonal detail and subtlties available within the range and captured by
> the data.

That is true as well...but...

> 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.

That is also true ;-)...but...

but...can your printing system reproduce all those tones, and if it could,
could you even see them?

You can't tell the difference between printing from an 8 bit file or a 16
bit file for color, and barely is there a difference in B&W.  Again,
remember, for color you have 24 bits, not just 8...so really, working with 8
bit color data is really indistinguishable in most all cases that if you
were to work with high bit data.  I still think you should do any large
tonal correction in high bit data, in the scanner driver and let the scanner
give you 8 bit data, or in PS, and then convert to 8 bit data if you want.

For B&W, you can actually, if you have a really good B&W printing system,
some difference in prints made using high bit data and prints made using 8
bit data.  It is VERY image and system dependant though, and the differences
are really barely perceptible to even the very trained eye, if using
something like Piezography.

Regards,

Austin

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