Digital BW, The Print

Hi Greg,

Thanks once again for your elaborate answer. 

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Greg" 
<dfaprinting@...> wrote:
> 
> The lightest inks can contribute to the darks areas, but why? WHy 
spray 
> all that solvent down when you can more effectively use a darker 
tone 
> to fill in between dots. Truthfully, with the RIPs I have used, I 
see 
> no need to ever have more than 2 inks going at a single time. 

Recall that I don't claim any hands-on expertise here. I'm just 
reflecting what I picked up here in the past. What I thought that was 
common sense is to have a number of jets firing simultanuously two 
reasons: 1) less dottier prints, 2) less microbanding.

If what you say is true, it's one argument less for a carbon-6 setup 
(note that I'm still in doubt whether to use carbon-6 or 4k+)
  
> Maybe this is different with QTR, I never really got very far into 
it.

I don't think this has anything to do with QTR. As a matter of fact 
the type of 2-jet curves you describe can be created with QTR very 
easily.


> Now, that said, if you want to use 3 heads firing at once, here is 
what 
> I would suggest. There is a point is each dilution where you get 
full 
> coverage, but not full density. Determine you maximum density, 
which is 
> the point were the paper can take no more ink, or more ink does not 
> give you more density. We will refer to this as the full amount, or 
> 100% (not the real 100% from the heads but 100% for the paper). Now 
> start with the lightest shade and work backwards (this is opposite 
from 
> the Epson way). Find the point where you reach complete coverage 
> (probably about half way to the cut off), and then you start to mix 
in 
> the next darker shade. You can slowly decrease the the amount of 
the 
> lightest ink, and decrease it until you get to the complete 
coverage of 
> the second shade. Now mix in the third shade following the same 
> pattern. All of this needs to be determined by density, not 
strixctly 
> by percentage. If you graph the density vs percentage sprayed on 
the 
> paper it will help you to figure this out. ANd if you graph the 
> percentage of ink on paper for the total of the two inks, you will 
get 
> some truly odd looking graphs.
> 
> How I arrived at the values was from the linarizing step in the RIP 
> which gives you the percentage of ink vs the measured density. Yes 
it 
> is a little obscure, but it sure did work for me. And I do realize 
that 
> describing it in words is a little difficult to translate between 
what 
> I say and what is really happening.

I think I understand what you try to explain. I made a model in excel 
to simulate what you describe above.

> And to make all this harder, the linearity of the full black is 
your 
> guide post. You need to mix the inks so that they end up doing the 
same 
> that the linearized full black is doing, otherwise you end up with 
a 
> non-linear output. 

This is actually rather logical, but why didn't I think of this 
myself?? I have been struggling to understand what the target ink 
load should be. But indeed a black-only curve can be used as 
guideline.

I think I'm done simulating. I have to make sure I get this Epson 
9000 and start making some real curves....

Joost