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Creating an icc profile with a densiometer.

Creating an icc profile with a densiometer.

2018-08-28 by per@...

Hi all, I have recently got hold of an xrite 810 densiometer, and I was hoping that I could use that with the QTR tool to create black and white icc profiles for my papers (I don't mind doing the readings of the target one by one). Is this possible to do? What format should the readings be put in? Any help much appreciated!

Re: [QuadtoneRIP] Creating an icc profile with a densiometer.

2018-08-28 by Simone Simoncini

Hi. I have the same. I got my readings in reflective , without color splitting, just the density value. You switch between transmissive and reflective by repeatedly pressing one button and between gray and color by pressing another (don't remember which is whoch at the moment).

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Il mar 28 ago 2018, 19:46 per@... [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> ha scritto:

Hi all, I have recently got hold of an xrite 810 densiometer, and I was hoping that I could use that with the QTR tool to create black and white icc profiles for my papers (I don't mind doing the readings of the target one by one). Is this possible to do? What format should the readings be put in? Any help much appreciated!

Re: [QuadtoneRIP] Creating an icc profile with a densiometer.

2018-08-28 by Paul Roark

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On Tue, Aug 28, 2018 at 10:46 AM per@... [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> wrote:

Hi all, I have recently got hold of an xrite 810 densiometer, and I was hoping that I could use that with the QTR tool to create black and white icc profiles for my papers (I don't mind doing the readings of the target one by one). Is this possible to do? What format should the readings be put in? Any help much appreciated!

Re: [QuadtoneRIP] Creating an icc profile with a densiometer.

2018-08-28 by per@...

Hi Simone, thanks for your answer. I understand how to get a normal density value readings from a step tablet out of the 810, but the part that I do not know is how to take the step tablet density values and put them in a form that is accepted by the QTR tool for creating icc profiles. The file format seems to be something written by some eye-one tool. Do you have any information on that?

Re: Creating an icc profile with a densiometer.

2018-08-28 by per@...

Hi Paul, I read this document and the accompanying file http://www.paulroark.com/BW-Info/Embedding_Photoshop_Curves_in_ICCs.pdf

Here are my questions 1) where do I find an .acv file for a p800 with stock inks; if I am supposed to make it, then how? 2) Given an appropriate .acv file, how to I print the step tablet? My intent is to use the ICC profile to correct the epson ABW mode, so do I just add the .acv to the step tablet and print with ABW as usual?

From that point on things seem straight forward. I was delighted to see you can input density values directly into the text file, and that the format was so simple.

Thanks for the useful information!

Re: [QuadtoneRIP] Re: Creating an icc profile with a densiometer.

2018-08-28 by Paul Roark

I think if you're going to use ABW, don't use curves. You might still be abel to use the linearization of the QTR app. (It's been a while since I've used this. So ...)

Paul
www.PaulRoark.com
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On Tue, Aug 28, 2018 at 2:12 PM per@... [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> wrote:

Thanks for your reply, PauI! I read this and the accompanying document at http://www.paulroark.com/BW-Info/Embedding_Photoshop_Curves_in_ICCs.pdf that you link to in this file.


My first question is where I would get an .acv curve file for a p800 with stock inks, or how should I produce a curve file like that? Second, given that curve, how would I print the step tablet with the curve? My goal is to apply this to the p800 in ABW mode, so would I just apply the curve to the step tablet image, and print with ABW as usual?

From that point on your document clarified a ton of things for me. For one, it is cool that you could just put density values directly in the text file!



---In QuadtoneRIP@yahoogroups.com, wrote :


On Tue, Aug 28, 2018 at 10:46 AM per@... [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> wrote:

Hi all, I have recently got hold of an xrite 810 densiometer, and I was hoping that I could use that with the QTR tool to create black and white icc profiles for my papers (I don't mind doing the readings of the target one by one). Is this possible to do? What format should the readings be put in? Any help much appreciated!

Re: [QuadtoneRIP] Re: Creating an icc profile with a densiometer.

2018-08-28 by per@...

Well, my goal is to make an icc profile, and it seems like people are being able to do so just by feeding the icc maker an output file from eye-one, and nothing else. If I make the density text file alluded to in your writeup and only feed that to the qtr icc maker, will that work? Or is the .acv necessary too?

Re: [QuadtoneRIP] Re: Creating an icc profile with a densiometer.

2018-08-29 by Paul Roark



On Tue, Aug 28, 2018 at 5:04 PM per@... [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> wrote:
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Well, my goal is to make an icc profile, and it seems like people are being able to do so just by feeding the icc maker an output file from eye-one, and nothing else. If I make the density text file alluded to in your writeup and only feed that to the qtr icc maker, will that work?

...


I think so. Give it a try.

Paul
www.PaulRoark.com
_,___

Re: [QuadtoneRIP] Re: Creating an icc profile with a densiometer.

2018-08-29 by John Isner

Can you create a text file in CGATS format from the EyeOne data? CGATS is the format expected by QTR-Create-ICC.
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On Tue, Aug 28, 2018 at 5:04 PM per@... [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> wrote:

Well, my goal is to make an icc profile, and it seems like people are being able to do so just by feeding the icc maker an output file from eye-one, and nothing else. If I make the density text file alluded to in your writeup and only feed that to the qtr icc maker, will that work? Or is the .acv necessary too?

Re: [QuadtoneRIP] Re: Creating an icc profile with a densiometer.

2018-08-29 by Simone Simoncini

I did not use the 810 to make icc. If I remember well you have to input cie lab values into the qtr make icc, so I do not think the 810 will be of any use for that purpose. It gives you the relative density for each colour RGB, but unless you are aware of a methodology to make the conversion between the two color models, those values are not usable.
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Il mer 29 ago 2018, 02:04 per@... [QuadtoneRIP] <;QuadtoneRIP@yahoogroups.com> ha scritto:

Well, my goal is to make an icc profile, and it seems like people are being able to do so just by feeding the icc maker an output file from eye-one, and nothing else. If I make the density text file alluded to in your writeup and only feed that to the qtr icc maker, will that work? Or is the .acv necessary too?

Re: [QuadtoneRIP] Re: Creating an icc profile with a densiometer.

2018-08-29 by roy@...

To use an ICC profile with Epson ABW driver you need to be on a Mac and use Print-Tool with
the "Epson ABW checkbox on". Print out a step wedge using No Color Management and some
appropriate selections in ABW driver. You can read the steps with a densitometer and just enter
the values in a text file on separate lines (i.e. 21 steps = 21 lines). Then run it through the QTR-Create-ICC
droplet app. (No .acv's, no linearize, no QTR driver curves).
Make sure when printing images to select the same ABW selections. (use Print Presets in driver).

Roy

Re: [QuadtoneRIP] Re: Creating an icc profile with a densiometer.

2018-08-29 by Simone Simoncini

Excuse me Roy, is it right that we need Lab values as input to the 21 step file ?
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Il mer 29 ago 2018, 09:06 roy@harrington.com [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> ha scritto:

To use an ICC profile with Epson ABW driver you need to be on a Mac and use Print-Tool with

the "Epson ABW checkbox on". Print out a step wedge using No Color Management and some
appropriate selections in ABW driver. You can read the steps with a densitometer and just enter
the values in a text file on separate lines (i.e. 21 steps = 21 lines). Then run it through the QTR-Create-ICC
droplet app. (No .acv's, no linearize, no QTR driver curves).
Make sure when printing images to select the same ABW selections. (use Print Presets in driver).

Roy

Re: Creating an icc profile with a densiometer.

2018-08-29 by brian_downunda@...

You can also do this on Windows, but there are a few traps to watch out for along the way.


---In QuadtoneRIP@yahoogroups.com, <roy@...> wrote :

To use an ICC profile with Epson ABW driver you need to be on a Mac and use Print-Tool with
the "Epson ABW checkbox on".

Re: Creating an icc profile with a densiometer.

2018-08-29 by per@...

Hi Roy, thanks for the quick reply. This is very encouraging. I am a windows user, but I will see if I can scrounge up a mac somewhere. That said, is there a difference between printing the wedge like this, and printing it using ABW mode from lightroom/photoshop (using "printer manages colors")? It seems like if I do this, then it will be sent to the printer without any color management too......

Re: Creating an icc profile with a densiometer.

2018-08-29 by roy@...

I'm not a Windows user (only Mac) but I think the issue is the same.

Epson's ABW was designed to be a non-color-managed workflow. In the
beginning Photoshop would have let you select a print icc profile and still
get to ABW in the Epson driver. In general this would be a mistake since
all provided icc's were for the color driver. To prevent people from inadvertently
doing this Epson and Photoshop got together to disable ABW when using
a print profile -- hence the "printer manages color" selection is necessary
if you want to reach ABW. This is actually a conversion to a fixed profile
(sRGB on the Mac).

When I wrote Print-Tool for the Mac I figured on the default case to be just
like Photoshop but I added the extra feature of allowing No-CM or an ICC
print profile and still getting to ABW. But it is special and does need special
icc's (ala Create-ICC). I'm not aware of an easy and straightforward workflow
accomplishing this for Windows but there may be one.
The other possibility is to make a Photoshop .acv Curve layer that you can
add to an image before printing. Not as elegant but works just as well.

Roy

Re: Creating an icc profile with a densiometer.

2018-08-30 by per@...

Thanks Roy for your reply! So what I am getting from your message, if I understand it correctly, is that it is fine to print the step wedge from photoshop with ABW mode and "printer manages colors". This will give me a wedge that I can measure where no monkeying has happened from the computer side and the printer has done its own stuff. Now, once I have an ICC profile, if I wanted to apply it, there is a simple way to do that through QTR for mac, but not windows. Correct?

I was not thinking of printing through QTR, my idea was instead to follow the flow from http://www.northlight-images.co.uk/print-setup-for-a-new-fine-art-paper/ described under "using a linearising profile". The idea, as described there, is to "take the monochrome (greyscale – profile Grey gamma 2.2) print-ready image, assign the QTR profile and then convert back to greyscale for printing" where printing here is taken to mean using photoshop with ABW mode. The idea, as far as I understand it, is to essentially rescale the image to offset the nonlinearity and then print with ABW like normal. Does this make sense to you?


Re: Creating an icc profile with a densiometer.

2018-08-30 by roy@...

I'd have to give a qualified "maybe". There are a bunch of subtleties in the background
and its really hard to tell if its all correct. In reading the north light article it seems
to me that the assign and convert are reversed in the description, but there are
quite a few details that are hard to be sure about. Unless you can personally see
the actual visible changes in the print with and without the workflow and they are
what you want to accomplish, I'm not at all sure it's worth it.

Roy

Re: Creating an icc profile with a densiometer.

2018-08-30 by brian_downunda@...

Sorry for being a tease, but I didn't want to clog the thread with unnecessary detail if there was no interest.

As Roy has described, Adobe don't make it easy to use ABW with ICC profiles. Party because they have a nasty habit of doing silent ICC conversions as part of the printing process.

I will concede that this is one of those instances where OS X is easier. The short Mac answer is to use Print Tool, which solves all those problems. On Windows you have to solve these Adobe-created problems yourself.

On Windows, to print with an ICC, you must:

1. Convert the image to the ICC in Photoshop.
2. Assign, NOT convert, the image to sRGB.
3. Print using Printer Manages Colours in the Photoshop print dialog.

You need step 3 in order to be able to access ABW in the printer driver settings. You need step 2, because Windows Photoshop (recent versions) will do a silent conversion to sRGB if you select Printer Manages Colours under Colour Handling, and so you need to fool Photoshop into thinking that it's already in sRGB. I have tested and measured this workflow and it works. I also tested leaving out step 2 and you get something odd.

So how do create the ICC in the first place? By taking the untagged 21x4 chart, or whatever chart you use to create a profile, and assigning it to Grey Gamma 2.2, converting it to AdobeRGB and then assigning (NOT converting) it to sRGB, printing it using ABW and the settings you'd normally use to print, and finally measuring and creating the ICC.

Is Mac easier? In this instance, yes. Is it worth changing to OS X just for this? Not for this little black duck.

The question I'd want to ask is, if you're going to all this trouble to measure and create ICCs for ABW, why not just use QTR(Gui)?

.................

If you want to read more about the silent sRGB conversion, here are two posts where I linked to a few threads on TOP. In the TOP comments section of those posts an Adobe software engineer, Dave Polaschek, discussed how Photoshop behaves on both Win and OS X under certain circumstances. Be warned, it's not easy reading.

My recollection was that you *could* print to ABW on OS X using by converting to an ICC and then selecting printer manages colours. The problem you may have is printing the untagged chart in order to create the ICC. My understanding is that on OS X, Photoshop does its silent ICC conversion on untagged images. But I haven't re-read those threads and I ain't a Mac guy.





---In QuadtoneRIP@yahoogroups.com, <per@...> wrote :

Brian, you tease. I am on windows, so I would very much like to know what these pitfalls would be.

Re: [QuadtoneRIP] Re: Creating an icc profile with a densiometer.

2018-08-30 by forums@walkerblackwell.com

If you are ICC profiling ABW, print the gray-gamma 2.2 (or sRGB/AdobeRGB) target with print-tool set to No Color Management and click the ABW button in print-tool (right next to the color management menu).

I have validated that this works although like Roy said, there is no guarantee that Apple/Epson won’t screw with the flow somewhere in the future.

Best and cheers,
Walker



> On Aug 29, 2018, at 11:43 PM, roy@... [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> wrote:
> 
> I'd have to give a qualified "maybe".  There are a bunch of subtleties in the background
> 
> and its really hard to tell if its all correct.  In reading the north light article it seems
> to me that the assign and convert are reversed in the description, but there are
> quite a few details that are hard to be sure about.  Unless you can personally see
> the actual visible changes in the print with and without the workflow and they are
> what you want to accomplish, I'm not at all sure it's worth it.
> 
> Roy
> 
> 
> 



[Non-text portions of this message have been removed]

Re: [QuadtoneRIP] Re: Creating an icc profile with a densiometer.

2018-08-30 by Mick Sang

I did that as well and found that it works with the same caveats.

 

Cheers,

Mick
Show quoted textHide quoted text
From: <QuadtoneRIP@yahoogroups.com> on behalf of "'forums@walkerblackwell.com' forums@... [QuadtoneRIP]" <QuadtoneRIP@yahoogroups.com>
Reply-To: <QuadtoneRIP@yahoogroups.com>
Date: Thursday, August 30, 2018 at 8:49 AM
To: "QuadtoneRIP@yahoogroups.com" <QuadtoneRIP@yahoogroups.com>
Subject: Re: [QuadtoneRIP] Re: Creating an icc profile with a densiometer.

 

  

If you are ICC profiling ABW, print the gray-gamma 2.2 (or sRGB/AdobeRGB) target with print-tool set to No Color Management and click the ABW button in print-tool (right next to the color management menu).

I have validated that this works although like Roy said, there is no guarantee that Apple/Epson won’t screw with the flow somewhere in the future.

Best and cheers,
Walker

> On Aug 29, 2018, at 11:43 PM, roy@harrington.com [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> wrote:
> 
> I'd have to give a qualified "maybe". There are a bunch of subtleties in the background
> 
> and its really hard to tell if its all correct. In reading the north light article it seems
> to me that the assign and convert are reversed in the description, but there are
> quite a few details that are hard to be sure about. Unless you can personally see
> the actual visible changes in the print with and without the workflow and they are
> what you want to accomplish, I'm not at all sure it's worth it.
> 
> Roy
> 
> 
> 

[Non-text portions of this message have been removed]

Re: Creating an icc profile with a densiometer.

2018-08-30 by per@...

Thanks for the very informative answer.

So why not just use QTRGui? Well, I'd be fine doing this if I could figure out how to make a custom paper profile for QTR using my densiometer. I don't feel I have the knowledge to write a description from scratch (I don't feel like I have the knowledge or understand the process to make the ink descriptions, but I would certainly be open to learning).

However, let me ask you this: Do you think that starting from a paper profile for my printer that seems similar to the paper I am using, and then using my densiometer to redo the gray curve and then linearize is a viable method? This seems doable.

Re: [QuadtoneRIP] Re: Creating an icc profile with a densiometer.

2018-08-30 by roy@...


---In QuadtoneRIP@yahoogroups.com, <forums@walkerblackwell.com> wrote :

>>>If you are ICC profiling ABW, print the gray-gamma 2.2 (or sRGB/AdobeRGB) target

This is an example of where you can go wrong if you are not knowledgeable and careful.
The targets are supplied in general with "no icc tagging" -- the idea being you are not to
use any color management. So if you change them in any way you must make sure not
the change the data values in the file. Assigning a profile is ok, but converting from grayscale
to RGB does do a convert -- you must to it in such a way that does not change the values.
A gray-gamma-2.2 to AdobeRGB is OK, but many are not. You can and should always
look at the histogram in Photoshop.

But the best answer here is NOT to mess with the target -- use the original file.
A correct target and no-cm doesn't look at the tagging (nor gray vs RGB) anyway.
Print-Tool with No CM will handle it all just fine. (Of course this is Mac only).

Roy

>>>with print-tool set to No Color Management and click the ABW button in print-tool (right next to the color management menu).


Re: [QuadtoneRIP] Re: Creating an icc profile with a densiometer.

2018-08-30 by Mick Sang

Extremely helpful advice, as always. Thank you.

 

Mick
Show quoted textHide quoted text
From: <QuadtoneRIP@yahoogroups.com> on behalf of "roy@... [QuadtoneRIP]" <QuadtoneRIP@yahoogroups.com>
Reply-To: <QuadtoneRIP@yahoogroups.com>
Date: Thursday, August 30, 2018 at 1:53 PM
To: <QuadtoneRIP@yahoogroups.com>
Subject: Re: [QuadtoneRIP] Re: Creating an icc profile with a densiometer.

 

  

 

---In QuadtoneRIP@yahoogroups.com, <forums@...> wrote :

>>>If you are ICC profiling ABW, print the gray-gamma 2.2 (or sRGB/AdobeRGB) target 

 

This is an example of where you can go wrong if you are not knowledgeable and careful.

The targets are supplied in general with "no icc tagging" -- the idea being you are not to

use any color management.  So if you change them in any way you must make sure not

the change the data values in the file. Assigning a profile is ok, but converting from grayscale

to RGB does do a convert -- you must to it in such a way that does not change the values.

A gray-gamma-2.2 to AdobeRGB is OK, but many are not.  You can and should always

look at the histogram in Photoshop.

 

But the best answer here is NOT to mess with the target -- use the original file.

A correct target and no-cm doesn't look at the tagging (nor gray vs RGB) anyway.

Print-Tool with No CM will handle it all just fine.  (Of course this is Mac only).

 

Roy

 

>>>with print-tool set to No Color Management and click the ABW button in print-tool (right next to the color management menu).

Re: Creating an icc profile with a densiometer.

2018-08-31 by brian_downunda@...

What inkset are you using and on which printer? My apologies if you've already mentioned this, but at a quick glance at your posts in this thread I couldn't see this info.

I use Piezography inks in an R1900 printer. IJM provide curves (.quad files) for this system, and if there isn't one for your combination of printer / paper / ink then you can take an existing Piezo QTR curve and relinearise it. (Note that I used the term "curve" - I reserve the term "profile" for an ICC profile.) Or you can buy (rent actually) the IJM Pro tools and create your own custom Piezo curves.

I also use QTR on an OEM 3880, and for that I use the curves that are shipped with QTR. For an unsupported paper I again take an existing curve for a similar paper and relinearise. Works surprisingly well in most instances. A lot of papers have the same or similar ink-receptive coatings.

If you're using an inkset other than Piezo or OEM, then others will have to assist. It's been a long time since I created a QTR curve from first principles. I'm sure Paul Roark and Richard Boutwell will only be too happy to advocate their approaches.


---In QuadtoneRIP@yahoogroups.com, <per@...> wrote :

Thanks for the very informative answer.

So why not just use QTRGui? Well, I'd be fine doing this if I could figure out how to make a custom paper profile for QTR using my densiometer. I don't feel I have the knowledge to write a description from scratch (I don't feel like I have the knowledge or understand the process to make the ink descriptions, but I would certainly be open to learning).

However, let me ask you this: Do you think that starting from a paper profile for my printer that seems similar to the paper I am using, and then using my densiometer to redo the gray curve and then linearize is a viable method? This seems doable.

Re: Creating an icc profile with a densiometer.

2018-08-31 by per@...

Stock p800 with stock inks. I'd love to use the piezography inks, but it seems less than straight forward (although another poster in this thread suggested refilling actual epson cartridges, which is an intriguing approach I will have to look into).

So in general, since there are plenty of p800 profiles for stock inks, what I take your message to mean is that I could just redo the linearization by taking the profile, taking out the existing linearization, printing a step tablet from QTR, measuring it with my densiometer, and then using the linearization applet to get data to put back into the file and this then should give me something close to optimal for my personal situation? If so, then that sound A-OK to me, and very doable.

Re: Creating an icc profile with a densiometer.

2018-08-31 by brian_downunda@...

A short answer is yes.

The P800 is a great printer for OEM QTR because as I understand it Roy has one and most reports I've seen suggest that a lot of the curves are very linear already and the neutral curves are quite neutral. People here can advise you which curves are good starting points if there isn't an existing curve for a paper you want to print on. Having said that, I just looked at the install and there doesn't seem to be a lot to choose from for the P800, so fingers crossed. Perhaps a P800 user or Roy can comment on the general applicability of those shipped curves. There were more for the 3880.

On the P800 you may find that you need to use the new 2880 Super resolution setting. Some people report banding at regular 2880, although TBH there's only one person who says this about printing on paper, most reports were from people doing digital negative on transparency, and those problems were fixed with 2880 Super.


---In QuadtoneRIP@yahoogroups.com, <per@...> wrote :

Stock p800 with stock inks. I'd love to use the piezography inks, but it seems less than straight forward (although another poster in this thread suggested refilling actual epson cartridges, which is an intriguing approach I will have to look into).

So in general, since there are plenty of p800 profiles for stock inks, what I take your message to mean is that I could just redo the linearization by taking the profile, taking out the existing linearization, printing a step tablet from QTR, measuring it with my densiometer, and then using the linearization applet to get data to put back into the file and this then should give me something close to optimal for my personal situation? If so, then that sound A-OK to me, and very doable.

Re: Creating an icc profile with a densiometer.

2018-09-06 by per@...

Thanks for your detailed answer Brian. I am finally getting around to testing this flow. Here are two questions:

1. When I print my test picture to measure, why is it necessary to convert to adobeRGB from the assigned gray 2.2? I understand that you have to force photoshop to think the picture is already in sRGB, but what does the conversion from gray 2.2 to adobeRGB do?

2. Assume I followed the flow to print a test ramp without ICC and created an ICC profile from the result. If I now wanted to check that the same ramp now is linear after correction, would I 1) load the untagged ramp, 2) assigning it gray gamma 2.2, 3) converting it to my ICC profile, 3) assigning it srgb, 4) print? Or does there have to be a conversion to adobeRGB too in there somewhere?

Kind regards,
-Per

Re: Creating an icc profile with a densiometer.

2018-09-06 by brian_downunda@...

1. You want to print the test picture without changing it, that is, without changing the underlying luminosity numbers. AdobeRBG also has a gamma of 2.2 and so for these purposes can be regarded as the RGB equivalent of Grey Gamma 2.2. If you look at the histogram when you convert from GG22 to AdobeRGB you'll see that the histogram doesn't change, just that you now have three channels rather than one. You need to do this in order to assign the picture to sRGB, because you can't assign a greyscale image direct to an RGB ICC profile, and you certainly don't want to convert it to sRGB - that's what you're trying to avoid Photoshop doing to it behind the scenes. Thus you need a two-step procedure.

2. In short, yes. You don't need to worry about the AdobeRGB conversion because you're intending to change the test ramp rather than trying to leave it unchanged. There is one qualification to this which I have failed to mention, and that is that the ICC that you create using the QTR tools will need to be an RGB profile. That is, you will need to use QTR-Create-ICC-RGB.exe rather than QTR-Create-ICC.exe. With an RGB profile you can then assign to sRGB, something that you couldn't do with one of QTR's greyscale ICCs.

Of course this convoluted workflow is only required to print to ABW on Windows using an ICC. The workflow for printing via QTRGui has none of this complexity. Well, almost none. Because QTRGui is not a colour-managed application, if you want to use an ICC to print, you'll need to convert the image to an ICC in Photoshop and save a copy for printing. This workflow is simpler on a Mac, because Print Took will allow you to print to either QTR or ABW using an ICC on-the-fly. Of course this raises the hotly-contested question about whether you *should* use an ICC for printing via QTR, but that's a separate question.


---In QuadtoneRIP@yahoogroups.com, <per@...> wrote :

Thanks for your detailed answer Brian. I am finally getting around to testing this flow. Here are two questions:

1. When I print my test picture to measure, why is it necessary to convert to adobeRGB from the assigned gray 2.2? I understand that you have to force photoshop to think the picture is already in sRGB, but what does the conversion from gray 2.2 to adobeRGB do?

2. Assume I followed the flow to print a test ramp without ICC and created an ICC profile from the result. If I now wanted to check that the same ramp now is linear after correction, would I 1) load the untagged ramp, 2) assigning it gray gamma 2.2, 3) converting it to my ICC profile, 3) assigning it srgb, 4) print? Or does there have to be a conversion to adobeRGB too in there somewhere?

Kind regards,
-Per

Re: Creating an icc profile with a densiometer.

2018-09-19 by per@...

So I finally got around to linearizing an existing p800 paper curve by 1) taking an existing p800 paper curve, 2) removing the linearization part, 3) printing a test ramp through QTR with the linearization-less resulting paper profile, 4) measuring it with my densiometer, 5) feeding that to the linearize app, 6) putting the result into the paper profile, 7) reprinting the ramp to verify the results. Unfortunately, when I am remeasuring the linearized profile ramp am seeing that it is not all that linear---the curve is decently linear from step 1 to step 15, but then it starts curving upwards.

So: Is this typical? It seems like I would want to linearize my linearization again.... What does one do in this situation?


Here is the resulting densities, if anyone cares. 0.06-.07 differences in the low densities, .2+ differences in the high densities.

0.04 0.1 0.15 0.22 0.28 0.34 0.42 0.5 0.57 0.65 0.75 0.85 0.95 1.07 1.2 1.34 1.47 1.65 1.87 2.12 2.58

Re: [QuadtoneRIP] Re: Creating an icc profile with a densiometer.

2018-09-19 by forums@walkerblackwell.com

This is showing as a curve because it is Density values (logarithmic). These density values correspond to pretty linear Luminance values though so you are ok.

Best,
Walker



> On Sep 18, 2018, at 10:37 PM, per@... [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> wrote:
> 
> So I finally got around to linearizing an existing p800 paper curve by 1) taking an existing p800 paper curve, 2) removing the linearization part, 3) printing a test ramp through QTR with the linearization-less resulting paper profile, 4) measuring it with my densiometer, 5) feeding that to the linearize app, 6) putting the result into the paper profile, 7) reprinting the ramp to verify the results. Unfortunately, when I am remeasuring the linearized profile ramp am seeing that it is not all that linear---the curve is decently linear from step 1 to step 15, but then it starts curving upwards.
> 
> 
> So: Is this typical? It seems like I would want to linearize my linearization again.... What does one do in this situation?
> 
> 
> Here is the resulting densities, if anyone cares. 0.06-.07 differences in the low densities, .2+ differences in the high densities.
> 
> 0.04
> 0.1
> 0.15
> 0.22
> 0.28
> 0.34
> 0.42
> 0.5
> 0.57
> 0.65
> 0.75
> 0.85
> 0.95
> 1.07
> 1.2
> 1.34
> 1.47
> 1.65
> 1.87
> 2.12
> 2.58
> 
> 
> 



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Re: Creating an icc profile with a densiometer.

2018-09-19 by brian_downunda@...

Since it was I who put you up to this ... There is a spreadsheet made available by IJM for checking linearity, which has a tab for luminosity data and one for density data. However the density tab has hidden columns that take the density data and convert it to luminosity and plot that rather than density, because the ideal QTR curve is linear in luminosity.

When I plot your data in the density tab of that spreadsheet the linearity is pretty good, as Walker said. Perhaps a touch light in the shadows. Someone who is ultra critical might do a second linearisation. I'm not sure I'd bother in this instance.

Re: Creating an icc profile with a densiometer.

2018-09-20 by per@...

Thanks! Richard has a spreadsheet that does a similar conversion that I have used in the past---I just did not realize that it was luminousity linearity I was after. It all makes sense now.

This begs the question though: If I was so inclined, how would I do a second linearization if I wanted? I see no place in the QTR curve editor to put second linearization data. Is there a way to combine two linearizations into a single one?

Re: Creating an icc profile with a densiometer.

2018-09-20 by brian_downunda@...

To be honest, if you're working with .qidf files .... I'm not sure. I guess it's possible but I'm not sure about the maths. Perhaps Roy or someone else could comment. Perhaps there's a trick that I've forgotten.

Because I am mostly a Piezography user I don't have .qidf files for my .quad files. Instead I use a droplet that Roy released a few years ago - QTR-Linearize-Quad.exe. You'll find it in C:\Program Files (x86)\QuadToneRIP\Eye-One. The idea is that you select both your measurement data file and the quad file in question and drag and drop them both onto this file and you get a relinearised .quad file with -lin appended to the name. If no-one offers you any suggestions about how to combine two linearisations then you could use this technique for a second round if and when you need it.

It's rare that a second round is required in my experience. If I have a difficult paper or one that I'm uncertain about, then I will try all the candidate curves - either MK or PK - and choose the one that's closest to linear to use for a relinearisation for the paper in question. In my experience what you want to try to avoid are curves with deep hooks in the shadows in their linearisation plots, since they don't relinearise all that well. In some case they won't relinearise at all - the underlying maths can't handle the shape.

Re: Creating an icc profile with a densiometer.

2018-09-21 by per@...

Well, I am just editing curves through the curve creator invocable from QTRgui on windows. When I look at the files that are loaded in the history of this tool, they are .qidf files. However, when I have edited a curve using the curve editor and saved it is seems it has only showed up as .quad files in the QuadTone/QuadP800 directory (not as new .qidf files) which is a little bit odd to me---especially as the tool pretends that there is a qidf file in the history of tool for the edited file.

Nevertheless, my linearized file exists as a .quad in the QuadP800 directory, and it seems that if I put new .quad files in the directory then they show up as usable curves in QtrGui. So your proposed flow seems workeable for me. I will have to give it a try. Thanks for the tip.

Re: Creating an icc profile with a densiometer.

2018-09-21 by brian_downunda@...

You can regard the .quad file as a compiled version of the raw code in the .qidf file (.txt file on a Mac). The .qidf file contains the basic parameters that define the curve and the .quad file contains the exact amount of ink that is applied from each channel for each luminosity level, which is what QTR uses to print. Piezography .quad files are generated from IJM's own software, and not from a .qidf.

Move to quarantaine

This moves the raw source file on disk only. The archive index is not changed automatically, so you still need to run a manual refresh afterward.