Digital BW, The Print

Hi Mike,

I know it sounds non-intuitive so I'll try to explain what is going on.

Take your 1024 stepwedge.   Somewhere there are 2 adjacent steps that have the
values 400/1024 and 401/1024.   When you print with IP you will get gray patches
that differ by some amount.   Take these two patches and to the little Levels/8bit/Levels
action I outlined to get 64 levels.  The 400/1024 pixels will all go to 100/256 or 25/64.
The 401/1024 pixels will go to 94% 100/256 and 6% 104/256  (or 25/64 and 26/64).
A 402/1024 would go to 88% 100/256 and 12% 104/256.   Note that it only uses
64 unique pixel values but the average can be pretty much any intermediate value
you want.  My contention and what I think I've demonstrated is it's the average value
over the whole patch that determines the "gray" value i.e. what you see and what you
measure with the spectro.  The fact that the pixels being averaged are not identical
values has absolutely NO affect visually or measured.

Try it out.  Take your 1024 discrete steps and do Levels action.  Note this is very
different than Posterize to 64 levels -- not at all the same.  You will still have 1024
discrete steps.   You will only tell the difference in that the file is 8 bit and the histogram
has lots of holes in it.   Look at it on the screen, print it on the paper, see if there's
anyway you can tell the difference.  I haven't tried it with IP but I'm pretty confident
that you will get the same result.

Roy

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Michael King" <drmrking@...> 
wrote:
>
> Roy,
> 
> If I do as you suggest, emperically I just can't see how its going to come
> out at more than 6 bits of step resolution.
> This seems to be no different to using a driver like ABW that only supports
> 8 bits of resolution and hence with ABW you only get 256 levels from the
> 1024 level wedge (basically every 4 steps come out at approx same value).
> 
> Note I understand that in a continuous tone gradient of 64 levels the
> dithering of the printer driver will create lots of levels and I guess I
> could easily find 1024 different levels. But I have a step wedge where each
> step is discrete and big enough to be measured independently by the
> spectro.  I am not looking for a random set of 1024 levels, I am looking for
> a specific stepping of levels of approx 0.1 L* between paper white and dmax
> 
> I think we are talking about two very different measurement scenarios, or I
> completely misunderstanding what is going on.
> 
> Mike
> 
> 
> 
> 
> On 19/11/06, Roy Harrington <roy@...> wrote:
> >
> >
> > Mike,
> >
> > I'm really saying more than that.
> >
> > --- In 
DigitalBlackandWhiteThePrint@yahoogroups.com<DigitalBlackandWhiteThePrint%
40yahoogroups.com>,
> > "Michael King"
> > <drmrking@> wrote:
> > >
> > > John,
> > >
> > > The current hardware (Epson x800) is already capable of printing a least
> > 10
> > > bits of gray (1024 levels) with IP (based on my own tests with a
> > spectro).
> >
> > The point is that you can get those 1024 levels with a 6 bit file. The
> > issue
> > arises because people say 6 bits = 64 levels so you couldn't represent the
> > 1024
> > levels. This isn't the way it works. ALL possible measurements that show
> > 1024 levels are averaging over an area with many pixels, so measuring more
> > than 64 levels is easily done.
> >
> > It would be great if you could take that exact setup with IP. Take the
> > file --
> > I presume it's a 16 bit stepwedge -- do the Photoshop operation I
> > specified
> > making it only have 64 grays. I maintain the file with look the same and
> > print
> > the same and when you measure it you'll still get 1024 levels.
> >
> > >
> > > Correct me if I am misquoting you Roy, but I think the point you are
> > making
> > > is that human vision probably struggles to perceive any difference in
> > images
> > > with more than 6 bits once you factor in PS dithering.
> >
> > Human vision will probably limit how far manufacturers will bother to
> > advance.
> > But my claim about # of grays is for your high end spectro, too.
> >
> > >
> > > Certainly without the dithering I think I can percieve more than 8 bits
> > > (around 9 bits) in a step wedge.
> >
> > I'm not sure what you would have in mind -- dithering is the ONLY way an
> > inkjet
> > print works. There is no other way. Dithering of the ink drops is needed
> > to
> > give a lot of grays in the print. The very slight dithering in PS is so
> > minor
> > compared to what happens in the driver/inkdrops/paper that the PS stuff is
> >
> > irrelevant.
> >
> > Roy
> >
> > > I'll do some more testing with dithered vs non-dithered images to see if
> > > there are real world situations that the dithering doesn't handle well.
> > >
> > > Mike
> > >
> > >
> > >
> > >
> > > On 19/11/06, john dean <deanwork2003@> wrote:
> > > >
> > > > Roy,
> > > >
> > > > I believe I understand most of what you are describing here. It seems
> > > > to confirm what you've said all along.
> > > >
> > > > I have two quick questions though. First, do you see the potential for
> > > > sofware rip advances that WILL allow us to gain output advantage in
> > > > sending bit depth larger than 8 bit to the printer in the near future?
> > > > And, second, are any of the new large format 12 channel pigment
> > > > machines that you've investigated addressing anything larger than 8
> > > > bit capability already?
> > > >
> > > > I guess what I am getting at is IF a bit depth beyond 8 bit WAS
> > > > possible in the near future, would we be seeing this capability coming
> > > > from new software, new hardware, or a combination of the two designed
> > > > in conjunction with each other.
> > > >
> > > > John
> > > >
> > > >
> > > >
> > >
> > >
> > > [Non-text portions of this message have been removed]
> > >
> >
> > 
> >
> 
> 
> [Non-text portions of this message have been removed]
>