Digital BW, The Print

Daniela,

I believe 4 shades are a safe bet, 3 may be problematic, and 5 may be 
overkill. It is important to note this depends on many variables; 
among them (1) printer droplet size, (2) printer driver (or RIP) 
which controls the dither, (3) relationship in color between the 
paper and the ink, and (5) viewer's visual acuity.

The modern Epson UC and K3 printer (and the older 1270, 1280 too)
drivers have a the capacity of very smooth prints, probably because 
of some proprietary dither algorithms. In comparison, the "Ordered" 
dither commonly used in QTR produces coarser prints, and therefore 
require more shades of gray. Try printing black only with QTR and 
compare with BO using Epson driver and you will see what I mean.

I am in the process of profiling right now, using the MIS UTFS (pure 
carbon) inks on a 2400 printer, using QTR. I have made custom 
dilution of the inks to increase the shades from the nominal 4 to 6 
shades. The papers I am profiling are Hahnemuhle William Turner and 
German Etching, both fairly warm tone papers. These papers are a 
wonderful color match to the pure carbon inks, and I must say that I 
see no visual reason to go beyond 3 shades when using 2880 
dpi, "better" options in QTR. For example at 60% ink limits, I start 
seeing the K (black) dots quite readily at 60% patch, which gets 
progressively worse at lower patches (brighter). The C (dark gray) 
dots become visible at the 55% patch. The M (medium gray) dots are 
virtually invisible even in the 5% patch. So, for this combination of 
printer, paper, ink, QTR at 2880 dpi, 3 shades are essential AND 
sufficient. My visual acuity (when I take my glasses off) is probably 
the equivalent of a 3X loupe; I focus on a 4x5 camera ground-glass 
without any aid.

Another note: If you are using QTR on the original UC (2200, 4000, 
etc) printers, you will (or at least I do) see dots when printing 
with "warm" curves, which use just 2 inks (K and LK). But curves such 
as "cool" or "cool-selenium" additonally use LC and LM inks, and the 
dottiness is definitely lower.

I hope this helps. Best regards and good luck.

Shilesh

--- 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/7
8918?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
>