Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "dgattarino"
<dgattarino@...> wrote:
>
> Thanks from the few of you who answerd my question.
> However, none of the replies mentioned the reason for the number they
> quote as the minimum number black inks for fine art B&W.
> I made a couple of considerations in the meantime:
> 1) The gray shades where the print start to look poor ar the lightest.
> That's where the dots from the print start to become visible.
> I have never seen such dots in the mid or dark tones
> 2) From a recent post from Clayton Jones
>
(http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint/messages/78918?threaded=1&m=e&var=1&tidx=1)
> it appears that the gray ink used by far the most is LLK. This means
> that LLK has to cover a larger range of tones by itself, when compared
> with the other gray inks. Therefore, it might need some "help" from
> another gray shade.
> 
> The above considerations would suggest that the minimum number of gray
> shade for best results is, infact, 4 with a LLLK supplementing Epson's
> LLK in the highlights.
> 
> I would like to know what you think about the above.
> Thanks. Cheers,
>    Daniela
>


I'll disagree slightly with this, while also agree slightly (how
redundant is this statement?). The way Epson did this was the same way
they do all their inks. They make the light inks do most of the work,
biasing the mixing toward the dark end. If they had used a lighter
light black, and lighter medium black, they would have been able to
get better highlights without needing as much color inks. However
doing this has some trade-offs in that you have a longer stretch where
the inks overlap, and this can produce higher ink loads on the paper.
This really comes into play when you are printing color and may have
considerable amounts of any two colors, plus considerable amount of
two black inks. The current Epson inks peak in density (on paper)
around the following (from a post by another member here about 3-4
months ago):
black - 100% (of course)
medium black - around 75%
light black - around 50%

So you still have a long space that the light black needs to cover,
and this of course requires the spacing between the dots in the
lightest shades. if you moved the light black to 25% max, and the
medium up to 50% max density, then you would get better coverage (more
ink on paper) up in the highlights, which gives a smoother tone. The
problem with this is that the full black will start to be dotty up
around 50%, so you would need to run increasing full black from 50% to
75%, as well as run the medium black for a longer period to get down
to the 75% density. The same will go for the light black to medium
black transition. When you start to look at the amount of ink on
paper, you may find that to produce a gray of 40% maximum, you need to
have the light black spraying almost at full capacity, and the medium
black at half capacity (or 150+% ink coverage). This really doesn't
mean much for neutral and lightly toned prints, but can really mean a
lot when you are doing color prints. And it is easier to understand
when you start graphing the density on paper vs. the amount of ink
being used.

So in short, you can get away with 3 carefully chosen black inks to
get really good results, but there may be a trade-off with the amount
of ink on paper. That's (one reason) why the Cone set uses 7 inks, the
amount of ink on paper is very consistent, and fairly small throughout
the entire density range until you get to full black ink. It allowed
the overlap areas to remain very short, where a 3 ink set might have
very long overlaps. 4 inks would reduce the amount of overlapped area
between any two shades, and if you run a 7 ink printer, you could
still have a real CMYK output.

This post has probably been more confusing than enlightening, sorry.