Digital BW, The Print

Roy,

> > > Tyler,
> > >
> > > Before responding to your post, I have one simple question for you.
> > >
> > > If the file only contains 256 levels of gray, and IF (BIG IF) what you
> > claim
> > > is true, that standard Piezo is capable of 1000 tones, where
> do the extra
> > > 744 levels of gray come from?  How, exactly, are they derived?
> > >
>
> Hi Austin,
>
> Sorry for joining late, but I've been away.
> Your arguments seem so self-evident that it hard to see what else is
> going on.  Say you were to create a 8 bit grayscale file with 256
> separate one inch squares such that each square contained a different
> gray value -- i.e. 0,1,2,... 255.  Each square has a different
> gray value and at least theoretically a different gray tone on the
> print --> thus there are 256 gray tones possible.  This is your
> argument, right?

No.  I simply do not believe the Piezo system prints more than 100 tones,
first off...and if I remember right, that is actually the original claim by
Jon when Piezo was first introduced...now it's magically jumped to 1000.
Secondly, I don't believe we can visually distinguish them, and thirdly, I
simply don't believe that the printers/inks/papers have the ability to print
1000 tones...the inks aren't that "pure", the ability to regulate the
droplets isn't that good...etc. to product 1000 distinguishable tones.

I completely understand residual tonality, that isn't the discussion.  There
simply isn't the tonal resolution (dynamic range if you will ;-) in the
system to print 1000 tones.  The noise is too high in the hardware alone to
make that possible.  Print a 100 step wedge, then try printing a 256 step
wedge...and measure it with the best densitometer you can find.  I guarantee
you won't get 256 separated tones, much less 1000.  The system works great
at around 100+, and that fits what we are able to see anyway...

> The tradeoff of gray levels versus resolution is really the entire
> basis of what's going on in printing.  Previously in this discussion
> there was distinction of pixels versus dots, but I think this is
> an unnecessary and misleading distinction.  Everything we have as
> far as Epson printers these days are pixels. The very smallest point
> on a print can contain any of 4 or 6 different gray/black inks drops,
> plus with variable droplet size and overprint of multiple drops,
> there are many possible gray values.  So I would call this a
> pixel not a dot.

Yeah, but it simply isn't a pixel, unless your "image" contains exactly the
values that are possible with the inks and droplet size (which is misleading
by the way), and the fact is, they don't.  The distinction between pixels
and dots is VERY important, or we would not be dithering, and the printer
driver does dither.

Austin