Re: Substrate Relativity Calculator
Re: Substrate Relativity Calculator
- Subject: Re: Substrate Relativity Calculator
- From: Michael Eddington <email@hidden>
- Date: Fri, 19 Oct 2012 08:33:16 -0400
Class brings up some good points, particularly points #2 & 3. With
regards to point #1, I think real world testing and application have
shown this method to have legitimacy.
> On Thu, Oct 18, 2012 at 12:40 PM, Claas Bickeböller
> <email@hidden> wrote:
>> Dear Mike,
>>
>> the underlying calculation method was originally developed and tested to predict the colour-deviation of a solid ink when the measurement backing is changed. BTW: For this purpose (solid inks and change of backing) it works very well.
>> Knowing this it is quite easy to understand what you will get from the calculation.
>>
>> If you have a colorimetric description of a print on paper 1, you feed this along with a whitepoint of paper 2 (or the same paper on a different backing, see above) to the calculation method
>> the model will predict the outcome of a print with constant density (remember, originally it predicts backing differences for the same print) on the new paper.
>>
>> So if you used this new dataset for imageseparation and proofing and if the printer printed with the same densities that he would have used for paper 1
>> you will have a match……… if the method worked.
>>
>> Things to consider:
>>
>> 1) The underlying model makes the assumption that the influence of the paperwhite on the resulting colour is linear from paperwhite to the blackpoint.
>> This assumption is simply wrong. So the predicted colours for everything but the solids is at least inaccurate if not completely off (depending on the inks, the screening…)
>>
>> 2) Is it a good practice to keep the densities that were found to fit perfect for one paper for another paper?
>>
>> 3) With increasing deviation between reference data-set and real-world paperwhite the prediction get's worse.
>>
>>
>> Regarding your question "acc. GraCol":
>> If you ask, if it was according to ISO 12647-7 (this is the international standard for digital proofing), the answer is yes, if the proof is in tolerance
>> when you compare reference printing condition (in this case the result of your calculation) and simulated colour on the proof.
>>
>> But what do you win, if you simulate something in tolerance that does not reflect reality…..?
>>
>> Best regards
>>
>> Claas
>>
>>
>>
>>
>>
>> Am 17.10.2012 um 19:39 schrieb Mike Stewart:
>>
>>> With papers changing the way they are; most do not fall within the
>>> tolerances specified in 12647-2. I like this idea of the Substrate
>>> Calculator. My question is this. Let's say we proof to GRACoL tolerances
>>> on a paper that is within the specification. We now get a #1 or #2 paper
>>> that is out of spec. I use the calculator, create a new CGATS file and
>>> create a new ICC Profile. I use CGS ORIS Color Tuner and hone in my
>>> proofing device (Indigo press) to within tolerance and proof my
>>> files/images on the "new" paper. What have I achieved. I have created a
>>> proof that the printer may have an easier time "matching"; but can I say
>>> that this proof adheres to GRACoL specifications? If you were to read the
>>> 12647 color bar it would pass only if I have the proper dataset loaded to
>>> compare to using software such as ORIS Certified Proof. Someone else
>>> checking my proof to GRACoL would say it "fails" because they would be
>>> comparing to the "original GRACoL". What exactly have I accomplished and
>>> how can it be classified as a specification.
>>>
>>> Mike Stewart
>>>
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>>
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