Digital BW, The Print

Hi Roy,

> > That is the one I thought you were using when you did your measurements
> > (21step)...but that's not a 256 step wedge.  What's the 256
> step wedge you
> > are referring to?
>
> Well a gradient in 8-bit is just the same as a 256 step wedge.

Doesn't that depend on how it's made?  A step wedge typically has defined
squares...and a gradient doesn't necessarily...but it does makes sense that
it would be made that way.

I believe the flush image may be a far better data source, if it is in fact
a 256 step wedge...and since I can't get PS to display grayscale in tonal
values, it's hard to test out.  You don't happen to know how to get PS to
display the actually pixel values...not just the %, which only gives me
discernability to %1...

> It not labeled
> as such but it does have all 256 levels (some do appear to be doubled) and
> far as I can tell there's no dithering between levels.

But if there's no dithering between the levels...then doesn't that refute
the 1000 tone claim...and support the less than 256 claim?

> >
> > BTW, do Rourke's "curves" print "more than 1000 tones" also?
>
> No real idea, but it is a more difficult question because there
> are so many
> different curves and they were all hand done and were somewhat limited
> by the max number of points in a PS curves.

I'm not quite sure what PS curves have to do with it...  Isn't the data
still sent to the printer driver, which only handles 8 bits anyway...but I
guess if it is in fact printing 8 bits/channel (and in this case, it
actually is), you could theoretically get the additional tones (though it
isn't 256 x 4 BTW, since you can't print all the way to %100 with three of
the inks...and some tones would be duplicated etc....which, this argument,
in and of it self, also brings me to question Cone's claim...since you'd
have to get 512 of the tones from the black ink only etc.).

> Here is Jon's
> > response...of course, it doesn't answer the question...
> >
> > "So if it could not and the smoothing was a bit choppy and the
> transitions
> > between tones was coarse and the eye could see all the breaks
> between the
> > overlapping inks and stuff like that - would you then say that
> PiezoBW looks
> > bad and it would need more tones to overcome those bits, and we
> would be on
> > the other side of the sun in a parallel universe doing the
> exact same thing
> > but just not as good and having a different discussion as to
> why we don't
> > use more tones than 256 so that the screening is not apparent, and the
> > overlapping inks is not noticeable, and that scaling is
> improved, and that
> > vignettes and blends are not blemished with digital artifacts
> and....... ;)"
> >
> > Sigh.  I don't believe you need 1000 tones to do any of
> this...that under
> > 200 would be perfectly enough.
>
> Well I suspect that 200 would be just barely enough and would have to be
> perfectly placed to be good enough.   Let's say that 100 tones are humanly
> discernable.  Seems to me that you need at least one more tone between
> each pair.  If two tones are discernable then a gradient from one to the
> other will have a posterized noticible transition.

I understand your point.

> With a tone in between
> you can smoothly go from one to the middle and then from the middle to
> the other tone.

Well, I don't believe that in images, which is what we're talking about, the
edges of the tones are that defined, and require the transitional "over
tones", but perhaps they do to some degree.  Also, the edges are "hard"...it
was meant to be that way, and I'd rather not have intermediate tones there.
But, I understand your point...and back to my point...I believe between 100
and 200 tones would work just fine.

Regards,

Austin