Digital BW, The Print

----- Original Message ----- 
From: "Roy Harrington" <roy@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Monday, June 16, 2003 5:31 PM
Subject: [Digital BW] Re: Alternative 8 >16 bit conversion, Grey
> CMYK conversion,


> Ernst,
>
> I agree that B is the only correct one and btw, what PS does.
>
> C is probably fairly harmless for most of the range,  but I
think
> at the end points you'll end up with some undesirable side
> effects.   Consider white=(8bit)0, if that gets converted to
> (16)bit0+random_number  its no longer white.  Its effect will
> be to increase dMin by half a unit and decrease dMax by
> half a unit.
>
> Roy

Roy,

Gert-Jan added later on that B is how PS does the conversion.

I got the impression that Gert-Jan suggested that if a conversion
like that has to be done then it is best to stretch the midtones
(add more random/noise to the middle than to the extremes) and
hardly the black and white. I have no idea whether there's any
improvement in the process.
One would think that noise in the image workflow normally builds
up higher in the extremes so diluting information in the middle
isn't a bad idea. I could ask him to add a changeable curve for
the distribution of the randomness, nice for experiments. Could
be a bit over the top too.

Keith,

I will ask for the greyscale to RGB conversion. It is all based
on libtiff routines he says so it will not be much work. The ZIP
compression is part of the libtiff features, it is supported in
PS like the other specs of it. This is Tiff 7 stuff that got its
specs described but hasn't had much promotion later on. The
Wasatch SoftRip doesn't take the ZIP compression after all so it
is of no use to me.

Antonis,

There's a Unisys licence issue of LZW in the USA. If it is kept
as a private affair and can be downloaded from Europe then I
don't see a problem.
For the moment I think there's no reason to put it on my site as
few will need a plain greyscale to CMYK converter anyway.

Ernst