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Ink separation test problem - Density goes up and then down for blacks

Ink separation test problem - Density goes up and then down for blacks

2015-10-03 by rafaelrojasphoto@...

Hi all!


I am new here and new using QTRip ... I have read all manuals and understood things, or at least I think I had! That being said, I am having really strange problems when printing the ink separation tiff file in order to calibrate the overall black ink limit and the gray inks density values.


Basically, when I make the print of the ink separation file, with 2880 dpi resolution and the right type of black chosen (matte black in my case), I obtain for the Black ink ONLY a strange phenomenon in the print: the density values increase up to the ink limit 70-75 % and then they decrease! That is, the density I observe (and mesure with a densitometer) decreases from 75% up to the 100 %.


Is there something I am doing wrong, or is just my printer gone crazy?


Thanks in advance for your kind help!


Warm regards,


Rafael

Re: [QuadtoneRIP] Ink separation test problem - Density goes up and then down for blacks

2015-10-03 by Paul Roark

​That's normal. That is why there is a black ink limit -- the high point in the density curve. Different papers can absorb differing amounts of ink. When they get overloaded the test patch will get a git lighter. Often there is a bit of a plateau at the top. The left edge of that plateau is where you want to have the ink limit (or black boost, but don't worry about that yet).

Paul
www.PaulRoark.com ​
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On Sat, Oct 3, 2015 at 12:03 PM, rafaelrojasphoto@... [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> wrote:

Hi all!


I am new here and new using QTRip ... I have read all manuals and understood things, or at least I think I had! That being said, I am having really strange problems when printing the ink separation tiff file in order to calibrate the overall black ink limit and the gray inks density values.


Basically, when I make the print of the ink separation file, with 2880 dpi resolution and the right type of black chosen (matte black in my case), I obtain for the Black ink ONLY a strange phenomenon in the print: the density values increase up to the ink limit 70-75 % and then they decrease! That is, the density I observe (and mesure with a densitometer) decreases from 75% up to the 100 %.


Is there something I am doing wrong, or is just my printer gone crazy?


Thanks in advance for your kind help!


Warm regards,


Rafael


Re: [QuadtoneRIP] Ink separation test problem - Density goes up and then down for blacks

2015-10-03 by rafaelrojasphoto@...

Hello Paul,

Thanks for your quick and enlightening answer.
Meanwhile I tested a different printer (a 3880) and I obtained the very same results with that same paper as with the 4900. As you mention, the density reaches a more or less plateau at values 65-70-75 and then the values start to get lighter again from 80 and on to 100. I assume that means I can select a value of ink limit for the blacks of around 60, with a black boost of 65.

Now, based on this effect, I do not understand why on his (great otherwise) manual, Tom Moore mentions using value of 100 for the black boost, which for instance for this paper I was testing today would provide a way lighter value than 65. More sense has the recommendation of Diallo Photography, where black boost is given a value of black limit + 5 more or less, or a value well in the plateau as you mention?

??

Rafael

Re: [QuadtoneRIP] Ink separation test problem - Density goes up and then down for blacks

2015-10-06 by Mike Finley

This is normal - that's why you need to set the black limit in the later 
steps in generating the ink curves.

On 03/10/2015 20:03, rafaelrojasphoto@... [QuadtoneRIP] wrote:
> Hi all!
>
>
> I am new here and new using QTRip ... I have read all manuals and
> understood things, or at least I think I had! That being said, I am
> having really strange problems when printing the ink separation tiff
> file in order to calibrate the overall black ink limit and the gray inks
> density values.
>
>
> Basically, when I make the print of the ink separation file, with 2880
> dpi resolution and the right type of black chosen (matte black in my
> case), I obtain for the Black ink ONLY a strange phenomenon in the
> print: the density values increase up to the ink limit 70-75 % and then
> they decrease! That is, the density I observe (and mesure with a
> densitometer) decreases from 75% up to the 100 %.
>
>
> Is there something I am doing wrong, or is just my printer gone crazy?
>
>
> Thanks in advance for your kind help!
>
>
> Warm regards,
>
>
> Rafael
>
> 
> ------------------------------------------------------------------------
> Posted by: rafaelrojasphoto@...
> ------------------------------------------------------------------------
>

-- 
mike finley photography
http://www.mikefinley.co.uk
http://words.mikefinley.co.uk

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