Digital BW, The Print

Keith,

I agree with you about the statement as written and always found it
misleading. Since the goal is to successfully simulate continuous tone all
you need is a number of tones greater than the minimum required to reach
that point. Like resolution, at a certain point, adding more doesn't result
in visible improvement.

I can at least see the idea 1000 shades of gray coming from the concept of 4
inks times 256 shades of gray. I agree with Tyler that this is theoretically
possible if the 4 inks differ in hue or chroma, and the driver is a 4
channel RIP processing a CMYK file. The actually number of colors would be
somewhere in between 256 and 1024 since the inks are partitioned over
different density ranges.

This is at the heart of the issue with grayscale inks. One of the things
that makes a toned silver print so wonderful is that it is not just shades
of gray but that it varies in hue as it varies in luminance. That is why I
am so fond of the MIS-VM and Selenium PiezoTone inks. They give you a
variation in color as they change in density. This is important because it
makes it easier for our eye to distinguish between different print
densities. Our eyes seem to be incredibly sensitive to slight color changes
near the neutral point which makes it difficult to get a truly neutral
print. What we want to do is to take advantage of that fact to enhance our
prints.

Lets say we can only distinguish X shades of gray but we want to represent
more then X shades in out prints. We can do this by using subtle variations
in the color of the shades and put the eye's fine color sense to work for
us.

For instance the Selenium PT inks appears to be a red-warm black and three
dilutions of a blue-cool dark gray. While I doubt there are 1024 "colors" in
the print, I think that are  more than the 256 you would get from a mono-ink
print. Remember that regardless of what type of file we send to the printer
it is still a 4 channel CMYK, 6 channel CcMmYK or  a 7 channel CcMmYKk
printer. I would guess that each channel receives at least an 8-bit data
stream from the driver.

The Lysonic E small gamut inks are another approach to this technique and I
would like to see something similar done with pigment inks. In theory the
2200 should be able to work in this direction as well and I will be
interested to see what people can achieve with it.

Martin Wesley

http://www.borderless-photos.de/guests.html



----- Original Message -----
From: "Editor P.O.V. Image Service" <editor@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Friday, August 02, 2002 10:21 PM
Subject: Re: [Digital BW] Do inkjets dither or not?


> Going back to the original...
>
> rmcooke wrote:
>
> >
> >In the August 2002 issue of the Digital Imaging Digest (which is
> >written by the folks at the PMA - Photo Marketing Association) they
> >cover quad tone printing among others and in the article they mention
> >Jon Cone's Piezography system.  They attribute the following quote to
> >someone from Cone's company:
> >
> >""Unlike the Iris process, PiezographyBW does not use a dithered
> >pattern. It is as close to silver properties as possible.
> >PiezographyBW's perceived resolution is greater than the human eye. It
> >renders more than 1,000 gray values in 8-bit mode.
> >
> I think the problem here is that if Jon is making prints with 1000
> luminance values he's gone totally nuts..  He must be marketing prints
> to CCDs, PMTs, and other sensors..
>
> > The new
> >PiezographyBW Pro24 renders more than 4,000 gray values in 16-bit mode."
> >
> >
> >
>
> Even more ludicrous..
>
> I think the fault probably lays with the publication in that the writer
> likely misunderstood Jon..
>
> There is no conceivable reason on God''s green earth to use 4000
> greyscale values, unless you like proving you can create things the eye
> cannot perceive..  In that case I would stop at 257 and be done with
> it.. LOL
>
> I would be willing to bet that Jon meant 4000 distinct RGB values on a
> print, when rendered from a 256 greyscale original...  That "more
> information is presented thereby to the human eye than one might get
> from a simple greyscale image"...  That would make sense..
>
> The statement as it is.. well.....  it's nonsense..
> Keith
>