Digital BW, The Print

Roy,

Thanks for your patience in trying to explain this. I am off to experiment
and see what happens in practice.
It may be a few weeks before I can report back as I travelling.

Mike


On 20/11/06, Roy Harrington <roy@harrington.com> wrote:
>
>
> 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<DigitalBlackandWhiteThePrint%40yahoogroups.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>
> <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]
> >
>
> 
>


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