Digital BW, The Print

> From: Bill Morse [mailto:willym@...]
>
> This is a curious statement.  If you look at the individual channels of an
> RGB scan of a B&W neg or print, you will see subtle but potentially
> significant variations in tonality.

If there are significant differences in tonality among the three channels,
then the image of the negative won't look monochromatic--you'll see actual
colors in it. I've never scanned a B&W negative, but I've certainly looked
at plenty, and I've never seen any sort of color cast in them.

> In addition, as Austin has said, one
> channel often will be more or less fuzzy, or the grain detail may
> be more or less pronounced.

My point was that that's probably the sort of thing that a good engineer
designing a scanner would have figured out, and handled automatically when
scanning B&W negs. But I could be crediting engineers with too much
intelligence.

> Finally, if there are any defects in the original
> (staining, scratches, etc.), they will often be more or less pronounced in
> the different channels.

That's a good point.

> One question- what leads you to say that using the channel mixer can
> \ufffdincrease the noise\ufffd of the image?

Only if different channels have different amount of noise, and you emphasize
or fail to de-emphasize the noisier channels. For instance, if the green
channel is quieter than the other two, and you select 33,33,33 instead of
0,100,0, you've got more noise than necessary.

--

Ciao,               Paul D. DeRocco
Paul                mailto:pderocco@...

>
> Regards
>
>
> Bill Morse
> PhotoProspect
> 450 Harrison Ave. Suite 221
> Boston, MA 02118
> (617) 868-7642
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