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Author Topic: completed first paper custom profile  (Read 22452 times)

digitaldog

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Re: completed first paper custom profile
« Reply #20 on: August 04, 2015, 03:43:57 pm »

I don't know how to do it in i1Profiler.   Preconditioning was discussed in Anders Toger's Inkjet printer profiling with Argyll and Colormunki tutorial that we have been referring to in this thread.
Skim it, but pay special attention to the Target generation details section, which explains why preconditioning may allow for a better choice of target patch colors.
I am just learning Argyll.  I have never used i1Profiler to profile and calibrate printers.  I would really like to read a comparison of Argyll and i1Profiler, done by somebody that knows color science well.
I was wondering what you guys were talking about.
I'd call the first step linearization, or at least a step used to build targets for a profile was historically called that. Maybe preconditioning is different?
I'd call the last step optimization, or at least a step to produce a better profile after initial profile creation.
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Iliah

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Re: completed first paper custom profile
« Reply #21 on: August 04, 2015, 03:56:21 pm »

I was wondering what you guys were talking about.
I'd call the first step linearization, or at least a step used to build targets for a profile was historically called that. Maybe preconditioning is different?
I'd call the last step optimization, or at least a step to produce a better profile after initial profile creation.
The idea of the "pre-conditioning" is to get a rough idea of the gamut and not to waste patches on sampling out-of-gamut; but rather, knowing the response, to place targets in such a way that the existing gamut is sampled better. Ideally "knowing response" also is "accounting for non-linearities", of course.

From help/manual on Argyll:

"The -c flag and parameter is used to specify an ICC ... pre-conditioning profile, for estimating perceptual distances and colorspace curvature, used in optimizing the full spread test point placement, or in creating perceptually spaced distributions. Normally a previous profile for this or a similar device will be used, or a simpler, preliminary profile will be created and used."

"To assist the determination of test patch values, it can help to have a rough idea of how the device behaves, so that the device test point locations can be pre-conditioned. This could be in the form of an ICC profile of a similar device, or a lower quality, or previous profile for that particular device. If one were going to make a very high quality Lut based profile, then it might be worthwhile to make up a smaller, preliminary shaper/matrix profile using a few hundred test points, before embarking on testing the device with several thousand."
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sgwrx

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Re: completed first paper custom profile
« Reply #22 on: August 04, 2015, 06:08:03 pm »

i did do the pre-condition, even though i don't fully understand it from the documentation.  but my question is: what if the profile you started with is very poor quality?  i guess that's when they say you can make a pre-condition target within Argyll comes in?

secondly, i'm not sure what's going on with the 2-step precondtion, but i'm guessing you run create a profile with precond set, then create another one using that second profile?

just a quick side question - you know the physical color checkers?  i have a lalrge one that's about 6-7 years old, but then i just got a new one with the colormunki photo.  my question is this: are the colors on these devices computer generated in LAB space with a certain lighting in mind like D50?  then they have to do some uber-color control in order to print it out or create a paint like substance to actually create the card?

so it all starts in the computer then and then gets translated into the physical world?
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Iliah

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Re: completed first paper custom profile
« Reply #23 on: August 04, 2015, 07:03:04 pm »

> i did do the pre-condition, even though i don't fully understand it from the documentation.  but my question is: what if the profile you started with is very poor quality?

The first, pre-conditioning, profile characterizes the borders of the gamut, and the device linearity. It allows for targen to follow something better than an abstract device model when generating patches for a final profile. Abstract model places the patches "all over the place", shooting in the dark. Pre-conditioning allows to put patches "on target", that is within the gamut of the device; and distribute those patches appropriately.

> i'm not sure what's going on with the 2-step precondtion

Just an improvement over the initial device description, plus if the first and second preconditioning profiles differ significantly, it is an early diagnostics of device instability or workflow problems (like not letting the target to dry fully, or wrong parameters in commandline).

> i'm guessing you run create a profile with precond set, then create another one using that second profile?

Yes.

> just a quick side question - you know the physical color checkers?

You mean, do I have those targets we shoot? Yes, I do.

> are the colors on these devices computer generated in LAB space with a certain lighting in mind like D50?

That is a long and very interesting story, you may want to start the reading with the bio of the man named Munsell, and his work of life. The colours are carefully selected from real-life colours and actually named after those colours, except some that are close to printing pigments (sort of real-life, too). The colours were coded in Munsell notation, and later converted to Lab (which is D50) for convenience.

> so it all starts in the computer then and then gets translated into the physical world?

From the above, you can see it is vice versa ;)
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sgwrx

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Re: completed first paper custom profile
« Reply #24 on: August 04, 2015, 07:42:27 pm »

thanks!

oh, so when a patch is named "skin tone" or "foliage" it's matching something real!  interesting, i'll do some reading tonight. thanks!
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Iliah

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Re: completed first paper custom profile
« Reply #25 on: August 04, 2015, 10:26:00 pm »

when a patch is named "skin tone" or "foliage" it's matching something real! 

There are 2 patches on ColorChecker Classic (24 patches) for the skin tone. One is "darker than light skin", the other is "lighter than dark skin".
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alain

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Re: completed first paper custom profile
« Reply #26 on: August 05, 2015, 03:54:40 pm »

> i did do the pre-condition, even though i don't fully understand it from the documentation.  but my question is: what if the profile you started with is very poor quality?

The first, pre-conditioning, profile characterizes the borders of the gamut, and the device linearity. It allows for targen to follow something better than an abstract device model when generating patches for a final profile. Abstract model places the patches "all over the place", shooting in the dark. Pre-conditioning allows to put patches "on target", that is within the gamut of the device; and distribute those patches appropriately.


Am I correct that a generic icc-profile from that paper/printer, for example from the manufacturer, could be used for the preconditioning?
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sgwrx

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Re: Re: completed first paper custom profile
« Reply #27 on: August 05, 2015, 04:31:45 pm »

Am I correct that a generic icc-profile from that paper/printer, for example from the manufacturer, could be used for the preconditioning?
yes. according to manual even something from a similar paper.  i used the generic photographique profile.  i bet i could have used ilford gfs profile.

Sent from my XT1080 using Tapatalk
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Iliah

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Re: completed first paper custom profile
« Reply #28 on: August 05, 2015, 05:06:40 pm »

Am I correct that a generic icc-profile from that paper/printer, for example from the manufacturer, could be used for the preconditioning?


I would not do that, it is a dubious shortcut. Some canned profiles are so far off that they do more harm than good.
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alain

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Re: completed first paper custom profile
« Reply #29 on: August 05, 2015, 05:37:19 pm »

I would not do that, it is a dubious shortcut. Some canned profiles are so far off that they do more harm than good.

Are the canned profiles so bad or are the printers still so different?

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Iliah

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Re: completed first paper custom profile
« Reply #30 on: August 05, 2015, 06:29:05 pm »

Are the canned profiles so bad or are the printers still so different?

Canned profiles are not very good. An error will cost 2x the work and time delays for drying, why take the risk.
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sgwrx

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Re: completed first paper custom profile
« Reply #31 on: August 05, 2015, 08:00:38 pm »

> i did do the pre-condition, even though i don't fully understand it from the documentation.  but my question is: what if the profile you started with is very poor quality?

The first, pre-conditioning, profile characterizes the borders of the gamut, and the device linearity. It allows for targen to follow something better than an abstract device model when generating patches for a final profile. Abstract model places the patches "all over the place", shooting in the dark. Pre-conditioning allows to put patches "on target", that is within the gamut of the device; and distribute those patches appropriately.

so what am i mis-understanding about pre-conditioning?  if you do not use (recommended to not use) a canned profile from the paper mfg. (aren't epson's supposed to be pretty good?),  then do you:

1. create a target w/o pre-conditioning, print it, measure it, create a profile (abstract device model as you say)
2. use this profile as pre-conditioning

?

i guess that makes more sense.  but since it's a characterization of the borders of the gamut, wouldn't pretty much any profile work?
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Iliah

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Re: completed first paper custom profile
« Reply #32 on: August 05, 2015, 10:37:22 pm »

> if you do not use (recommended to not use) a canned profile from the paper mfg. (aren't epson's supposed to be pretty good?),  then do you:

> 1. create a target w/o pre-conditioning, print it, measure it, create a profile (abstract device model as you say)
> 2. use this profile as pre-conditioning

Yes. Epson profiles are supposed to be good, and they are good; but in practice, I specifically checked that, creating a pre-conditioning profile from the scratch works better. However please keep in mind, my spectrophotometers are automatic, so I do not care how many patches I need to measure. Another thing with me is that I seldom go for shortcuts. I do not want anybody to get side-tracked into splitting hairs; just describing how I do it.
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sgwrx

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Re: completed first paper custom profile
« Reply #33 on: August 06, 2015, 12:00:06 pm »

ah ok, makes more sense to me. thanks!  so yeah, if the profile is bad it'd not be as good.  so the best approach is to "shoot in the dark" as far as which patches are made automatically, then use that to hone-in.

i'm probably going to try 800 or so patches this week or next just to see how it goes for myself.  i'll do it this way for preconditioning.  that'd be 4 a4 sheets of paper. though i thought i read somewhere i could print the same size patches on 13x19 paper and get more of them on that paper. i'll read up on that.
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