Digital BW, The Print

Hi Austin,

> 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.

Yes, using the gradient tool without dithering will make squares, with dithering
it will actually smooth between transition.

> 
> 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...

I see Tyler has already mentioned the RGB way to look.  Its also unfortunate
that you can never see the low bits in 16 bit mode.  The trick to see what
PS is doing is to select a smaller area and run Adjust Levels and bring the
white and black points way it.  It increases the contrast to make it easy to
see.  If you separate the W & B by a power of 2, you left shift the pixel
values by that many bits.  Recently someone mentioned that PS only uses
15 bits in high bit mode, I was able to confirm this using this method.

> 
> > 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?

As I said above, the dithering/no-dithering gives you the steps versus
smooth transition.  I'd hope you could try both and see the results.

> 
> > >
> > > 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

Its just that PS limits how accurate you can specify the adjustment curve.

> 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.).
> 
> 
> 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

Roy