You are speaking of what is referred to as "dot gain". The picolitre
measurement is not a size, per se, but a volume of ink. Therefore the
dot gain of the paper will determine the size of the "flat" dot. Plain
paper certainly has a fairly large dot gain, but specially coated inkjet
papers are designed to control dot gain. You are correct that some use
dot gain to "smooth" the edges of the dots, but they do not typically
"fill in" the whole area other than in darker areas. The dots typically
are found intermingled with one another and with some white paper
substrate.
Take a look as a print under a loupe and you'll see.
Dye inks tend to have higher dot gain than pigment color inks, because
they are designed to penetrate and spread in the fiber of the paper
which pigments sit on top of the paper for the post part. It all comes
down to careful control on the dot volume. They is in part why profiles
are created for different paper types.
There is a certain loss of color fidelity or accuracy with a four color
system (even one with low dye load inks). That is why many inkjet
manufacturers have added greens or blues, oranges or reds. The making
of blue from cyan and magenta, and red from magenta and yellow somewhat
limits the gamut available, so by adding a "true blue and red, or green
and orange, often allows for several advantages. Less dots have to be
laid down since, for instance, every blue dot is equivalent to several
cyan and magenta dots. That speeds up the printing process. Further,
the blue might be one that is out of gamut for a mix of magenta and
cyan. It is also more profitable for the inkjet company, since they
sell a lot more ink cartridges when the printer has 7 or 8 or more
involved. It also makes counterfeiting or 3rd party copies more
difficult, and makes the profiles more "ego-centric" to the specific
colors of the OEM inks.
Overall, for most applications, however, the idea of a simple four color
printer using a very small dot size and 4 full dye load inks, makes
sense in terms of use of raw materials, and fade resistance.
Art
SleeperMan wrote: