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Author Topic: An academical question regarding to color adjustment  (Read 1173 times)

aaronchan

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An academical question regarding to color adjustment
« on: November 27, 2020, 06:34:40 am »

Dear all,

Let me just dive into it right away.
Let's say I have used advanced black and white mode with a custom color toning.
Then, I print out a grayscale target (129 steps) and a normal image.
Scan the target with i1pro so now I have a LAB measurement of this specific tone.

How can I use this measurement and re-create the tone precisely in photoshop and print it out with a proper color icc profile?

I hope you guys can understand what I'm talking about.

Thanks
Aaron

digitaldog

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Re: An academical question regarding to color adjustment
« Reply #1 on: November 27, 2020, 12:01:31 pm »

No. ABW is a black box.
Profiling requires a reference AND resulting measurements and what you propose is akin to one hand clapping.
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Doug Gray

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Re: An academical question regarding to color adjustment
« Reply #2 on: November 27, 2020, 05:32:58 pm »

Dear all,

Let me just dive into it right away.
Let's say I have used advanced black and white mode with a custom color toning.
Then, I print out a grayscale target (129 steps) and a normal image.
Scan the target with i1pro so now I have a LAB measurement of this specific tone.

How can I use this measurement and re-create the tone precisely in photoshop and print it out with a proper color icc profile?

I hope you guys can understand what I'm talking about.

Thanks
Aaron

Do you wish to make a print of a B&W image (in some RGB space where R=B=G) that will look the same as what you printed using ABW with a selected tint? And you wish to do this with using the standard, color managed printing using the regular color driver and associated profile?

Or do you wish to make a profile that can let you visualize the tinted B&W in Photoshop which you will then print in B&W mode?

If this isn't what you want please expand on what you did and are now trying to do.

The fundamental problem is that printing in B&W mode isn't controlled by a user selectable profile for most printers.

Take a look at this:
https://github.com/doug3236/ABWProfilePatches
« Last Edit: November 27, 2020, 05:37:38 pm by Doug Gray »
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aaronchan

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Re: An academical question regarding to color adjustment
« Reply #3 on: November 28, 2020, 01:53:57 am »

No. ABW is a black box.
Profiling requires a reference AND resulting measurements and what you propose is akin to one hand clapping.

Maybe I didn't make myself clear. (English isn't my first language)
So I have made a print with ABW, color toned. On the print, there is a 129 steps target.
I measured the target, and that is my aim.
And now, I want to mimick my "original neutral gray" 129 steps target, print out with a RGB ICC profile and get the same result as my toned B&W print with ABW.
Is that more clear?
I've tried to use my measurement with CTPro and make an abstract profile. But seems like that doesn't do much to simulate my ABW print.

digitaldog

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Re: An academical question regarding to color adjustment
« Reply #4 on: November 28, 2020, 09:41:40 am »

ABW does not print using all inks, RGB ICC does. That fact alone I'd stick with my original answer.
I suppose anything is possible given enough time and wasted ink and paper, why?
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Doug Gray

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Re: An academical question regarding to color adjustment
« Reply #5 on: November 28, 2020, 01:28:18 pm »

Maybe I didn't make myself clear. (English isn't my first language)
So I have made a print with ABW, color toned. On the print, there is a 129 steps target.
I measured the target, and that is my aim.
If you have the measurements, just fill in the 129 step target image that's first assigned to an RGB colorspace like Adobe RGB, with the L*a*b* values from the measurement.
Quote
And now, I want to mimick my "original neutral gray" 129 steps target, print out with a RGB ICC profile and get the same result as my toned B&W print with ABW.
Then you have an image that looks like your print. It can be printed in regular color mode using Abs. Col. to re-create the same printed image.
Quote
Is that more clear?
I've tried to use my measurement with CTPro and make an abstract profile. But seems like that doesn't do much to simulate my ABW print.

An abstract profile could work but I don't know of anyone that has published such a process. However, the ICC profile created by the program in my github link can be used to create an image of a ABW print in a standard working space including Lab by the following process:

1. Convert a B&W image in an arbitrary colorspace (Adobe RGB, sRGB, etc) to rgb device space using the B&W icc profile created by the github program in Photoshop.

2. Then convert back to Lab, or any desired RGB colorspace using either Abs. or Rel. Col. depending on whether you want the white patch scaled to L=100 or to actual paper white.

You can then view or print the image using either Abs. or Rel. Col. depending on what you selected earlier. It will match the print using ABW. At least to the extent your standard ICC printer profile is, itself, accurate.
« Last Edit: November 28, 2020, 01:32:51 pm by Doug Gray »
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digitaldog

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Re: An academical question regarding to color adjustment
« Reply #6 on: November 28, 2020, 01:31:49 pm »

"You can do all sorts of things that are fiendishly clever, then fall
in love with them because they're fiendishly clever, while
overlooking the fact that they take a great deal more work to obtain
results that stupid people get in half the time*. As someone who has
created a lot of fiendishly clever but ultimately useless techniques
in his day, I'd say this sounds like an example.
"
Bruce Fraser

*Using ABW.  :D
Let's not lose sight of the specific question: can I use this measurement and re-create the tone precisely in photoshop
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Doug Gray

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Re: An academical question regarding to color adjustment
« Reply #7 on: November 28, 2020, 01:53:46 pm »

ABW does have it's uses.

1. It produces more stable prints because it uses less CYM with much more Ks. Less color shift over time with exposure to the elements.

2. It produces more consistent L* values. I created a process for making ABW icc profiles because I needed maximum accuracy when creating special reflectance targets for a company I was working with. ABW produced more consistently precise patches of specified reflectance than the same ones printed using normal color managed processes.  A side effect is that it also does a great job of soft proofing ABW prints.
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aaronchan

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Re: An academical question regarding to color adjustment
« Reply #8 on: November 28, 2020, 11:01:52 pm »

ABW does not print using all inks, RGB ICC does. That fact alone I'd stick with my original answer.
I suppose anything is possible given enough time and wasted ink and paper, why?

How about this, instead of ABW, let me put it in this way. Cyanotype.
Let's say I have 129steps lab measurement of a cyanotype print.
Now that I want to use this measurement to make my inkjet print looks like it.
Is it possible to do what I wanted to do but without doing any manual curve adjustment in photoshop, just by using the measurement that I have.

digitaldog

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Re: An academical question regarding to color adjustment
« Reply #9 on: November 28, 2020, 11:08:15 pm »

How about this, instead of ABW, let me put it in this way. Cyanotype.
Let's say I have 129steps lab measurement of a cyanotype print.
Now that I want to use this measurement to make my inkjet print looks like it.
Is it possible to do what I wanted to do but without doing any manual curve adjustment in photoshop, just by using the measurement that I have.
I really don't understand what you are talking about.
You have a process (ABW or Cyanotype) that produces what you want; use it.
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aaronchan

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Re: An academical question regarding to color adjustment
« Reply #10 on: November 28, 2020, 11:52:12 pm »

I really don't understand what you are talking about.
You have a process (ABW or Cyanotype) that produces what you want; use it.
Sometimes, curiosity could lead you to many possibilities.
I do always say that, if you like the look of the film, shoot film.

If you ask me why I would say that might be possible to preserve the look of some unique process.
Dye transfer has been gone for some time. All we can do is to scan/capture what we have and reprint them.
But what if we have enough data/measurement of this process, can we mimick it by using another technology such as inkjet to recreate the look of it? Why not?

Doug Gray

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Re: An academical question regarding to color adjustment
« Reply #11 on: November 29, 2020, 12:03:35 am »

How about this, instead of ABW, let me put it in this way. Cyanotype.
Let's say I have 129steps lab measurement of a cyanotype print.
Now that I want to use this measurement to make my inkjet print looks like it.
Is it possible to do what I wanted to do but without doing any manual curve adjustment in photoshop, just by using the measurement that I have.
There is no simple way to do this. To be possible at all you would need to additional information.

Besides the Lab measurements of the 129 patch print, you also need the originating RGB and reference colorspace, or (gray scale with dot gain) values that the 129 patches came from. If you have both sets then it's possible. Otherwise it isn't. What colorspace is the image with the 129 patches in? For instance, sRGB with values of (0,0,0),(1,1,1),(3,3,3),(5,5,5)...(255,255,255)

If you make a post and attach a zip file containing both sets of data I'll see what's possible.
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aaronchan

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Re: An academical question regarding to color adjustment
« Reply #12 on: November 29, 2020, 12:27:44 am »

There is no simple way to do this. To be possible at all you would need to additional information.

Besides the Lab measurements of the 129 patch print, you also need the originating RGB and reference colorspace, or (gray scale with dot gain) values that the 129 patches came from. If you have both sets then it's possible. Otherwise it isn't. What colorspace is the image with the 129 patches in? For instance, sRGB with values of (0,0,0),(1,1,1),(3,3,3),(5,5,5)...(255,255,255)

If you make a post and attach a zip file containing both sets of data I'll see what's possible.

Thanks Doug, I'll get that to you on Monday when I'm back to my computer.
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