On Sunday, July 18, 2004, at 08:42 PM, Clayton Jones wrote:
> Hello Paul,
>
>> If I print a test target in NCA mode on my 2200, the 0,0,0 patch
>> generally looks a tad lighter than the nearby black patches. It
>> appears that 0,0,0 translates into pure K, while other small
>> values produce CMYK combinations that are actually darker. I would
>> think that good profiling software would be smart enough to avoid
>> pushing the printer into its pure K output range,
>> but apparently it isn't.
>
> I'm not sure what you mean by "CMYK combinations" when I'm printing BO
> from only the black cart. Doesn't that mean combinations of various
> inks?
>
> I have been working with the assumption that in a grayscale mode image
> a pixel of 0 RGB value is as black as is possible, and that a patch of
> 0 pixels will be printed with the blackest ink combination that the
> printer is capable of (which in a BO print would be 100% coverage of
> dots).
>
> The big assumption is that more ink was laid down in the 2nd print.
> Based on that:
>
> I was talking with Steve K. about it today and we wondered what there
> was about the paper that would make the patch look darker the 2nd
> time, when the first print had what looked like 100% coverage. It
> would mean the paper is capable of looking darker with that extra ink
> (up to a point I suppose). That would mean that the quantity of ink
> is a factor as well as 100% coverage of dots. Some questions:
>
> 1) Why did the S-curve, which didn't move the zero anchor point and
> theoretically didn't change any already zero pixels, make the printer
> put down more ink in a patch that was already solid zero pixels?
>
> 2) What does "more ink" actually mean in this case? Two squirts on
> each dot location instead of one? Dot locations that overlap?
>
> 3) Why does adding more ink to an already 100% covered area of pure
> black increase Dmax? Does a lesser amount of ink sink in deep and
> leave less on the surface, and a greater amount "fills it up" so to
> speak?
>
> 4) Will all papers react to extra ink that way?
>
> 5) Here's the biggie: The paper is capable of much better Dmax if you
> give it more ink. I found that I can give it more ink with the curve
> (for whatever mysterious reason), but it ruined the pic because the
> rest of the image was too contrasty. How can I make the printer give
> it more ink in zero RGB zones without changing the contrast?
>
> One reason I'm so interested is because the paper in question has
> paper color and ink color that are nearly identical to Photo Rag, but
> considerably less Dmax. But the 2nd print was so much closer to PR
> that it could easily become a PR substitute at a far lower cost and,
> from my testing so far, without the flaking problem. But how to get
> more ink to the paper in the black areas...
>
> Thanks for the input.
>
> Regards,
> Clayton
>
>
> Info on black and white digital printing at
> http://www.cjcom.net/digiprnarts.htm
>
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