Digital BW, The Print

> Ernst,
> 
> I'm not sure I understand your comments.  With inkjets there's no notion 
> of dot shape -- they are just drops out of the piezo jet.  I agree that smaller
> dots have slightly more dotgain but the linearization and/or gray ICC profile
> measure the actual densities and compensate for any dotgain differences.
> 
> I have some of Paul prints and my feeling with them is more of an overall
> sandpaper feeling if you get up close to it.   One effect that may be happening
> in the midtones is that there are two pseudo random dithering patterns from
> two inks overlaid.  The interaction is more truly random giving the possibility
> of dot doubling/clumping on a minute scale.  (it's a little like moire patterns but 
> there's no overall regularity).   It may be this randomness however that helps 
> get rid of banding side effects.
> 
> Roy

Roy,

whatever dot distribution you select random or ordered 
there's a point with BO only where half the paper is black 
and half is white. To reduce the dotgain effect at that 
point to a minimum one would prefer a line screen of black 
and white lines and the lines as thick as possible. Horrible 
for detail and a very dominant pattern. Any compromise to 
get more detail and less visibility in the pattern results 
in smaller dots and  more complicated patterns including 
random dot distribution. That will increase the influence of 
dotgain whatever pattern is selected and around 50% the 
patterns are sensitive to that influence, little dotgain has 
  a lot of influence then. Profiling should deal with that 
but climate control in the list members houses still gives 
variables. Another variable is the paper coating per batch, 
the printer's condition and printing smaller prints on an A3 
printer speeds up the printing while the drying time isn't 
increased. Individual printers vary so a general profile 
will lead to different  results. In quad ink sets much of 
this tone effect is dampened by the diluted inks, it will 
not be like that in BO printing whether with one or multi heads.

I think that with BO more attention has to be given to 
regular linearising of the ink set. Multihead BO suppresses 
the effects of  banding, nozzle defects etc but isn't an 
answer to dotgain, it actually will increase the influence 
of dotgain as it forces the heads to the use of the smallest 
droplet for the resolution selected. Expect a lot of 
different opinions on what list members get from their 
printers on BO, not just a matter of taste for BO but also 
real differences in the prints with everything else being equal.

It isn't that I'm against the method but when I wrote about 
it 4 years ago I immediately realised that it could have 
that negative effect too. I was also a bit worried about the 
"CMYK" dot distribution that might not be the best KKK dot 
distribution. Related to that dotgain effect. I'm curious 
what practice will tell us, few users right now.

Met vriendelijke groeten,  Ernst


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