Discussion: View Thread

I'm a content creator tasked with establishing color profile settings for my employer, as relates to all Adobe CC apps. We regularly provide print-ready PDF to a variety of print providers, including offset, flexo, and digital hybrid. 
I've chosen Adobe RGB for our created print-ready RGB images, and selected GRACoL2013-C1 (CGATS21-2 CRPC6) for CMYK.
My question has to do with the setting for grayscale.
The various standard profiles (for example North America General Purpose 2) provided indicate Black default as 20% Dot Gain, and the same for Spot colors.
Wouldn't I want to set my Black profile to match the cmyk profile (in this case it would display as "Black Ink - CGATS21_CRPC6.idd in Photoshop Color Settings) so that this color behaves the same throughout the remainder of the production process?  [See attached screen cap for these settings]
In other words, if the black channel in a cmyk image is 50% tint (which passes through into my PDF) wouldn't I want my 50% gray tinted graphic to carry the same profile? 
I can understand spot colors playing by the 20% dot gain rule, as those colors could be controlled on press independent of the cmyk. But the black channel is ultimately shared by both cmyk and grayscale images, and when we have cmyk images we are also likely to have gray images in the document, too. Shouldn't their profile settings match?
I'm fully open the idea that I'm thinking too hard about this, but I do want to get it right and not just by flipping a coin for each setting.
Thank you for your input -- it is valued and appreciated. ​​

------------------------------
Brett Stone
Owner
Yfficient Graphic Design and Marketing
Saint Charles MO
------------------------------

Brett,

You are 100% correct.

Don

Don Hutcheson
don@...
908-500-0341
(Typos courtesy of iPhone's teeny-tiny keyboard and not-so tiny thumbs)


Original Message------

I'm a content creator tasked with establishing color profile settings for my employer, as relates to all Adobe CC apps. We regularly provide print-ready PDF to a variety of print providers, including offset, flexo, and digital hybrid. 
I've chosen Adobe RGB for our created print-ready RGB images, and selected GRACoL2013-C1 (CGATS21-2 CRPC6) for CMYK.
My question has to do with the setting for grayscale.
The various standard profiles (for example North America General Purpose 2) provided indicate Black default as 20% Dot Gain, and the same for Spot colors.
Wouldn't I want to set my Black profile to match the cmyk profile (in this case it would display as "Black Ink - CGATS21_CRPC6.idd in Photoshop Color Settings) so that this color behaves the same throughout the remainder of the production process?  [See attached screen cap for these settings]
In other words, if the black channel in a cmyk image is 50% tint (which passes through into my PDF) wouldn't I want my 50% gray tinted graphic to carry the same profile? 
I can understand spot colors playing by the 20% dot gain rule, as those colors could be controlled on press independent of the cmyk. But the black channel is ultimately shared by both cmyk and grayscale images, and when we have cmyk images we are also likely to have gray images in the document, too. Shouldn't their profile settings match?
I'm fully open the idea that I'm thinking too hard about this, but I do want to get it right and not just by flipping a coin for each setting.
Thank you for your input -- it is valued and appreciated. ​​

------------------------------
Brett Stone
Owner
Yfficient Graphic Design and Marketing
Saint Charles MO
------------------------------

You're 100% correct as Don points you but.... you can forget about it. If you look internally to "Black Ink - CGATS21_CRPC6.icc" and to "Dot Gain 20%.icc" you'll see both are "identical" profiles (except by a little difference I'll mention later on). You can compare them just in PhotoShop (loading them in Gray ColorSpace and then looking to the curve going to custom) or in a match easy way just opening both profiles in ColorSync utility (in a Mac) or with ICC Profile Inspector in a PC. You'll see the KTRC curve (this is a GrayScale profile so it doesn't contain A2B or B2A tables, only curves) is the same one. Ok, you'll note it's starting in a different point (DG 20% starts in x,y 0,0 while Black Ink from CGATS21 starts in x,y 0,2.4) but this is because also the White Point in both profiles is set in a different way and even more this will be only considered if you use Absolute Colorimetric RI.

So basically if you convert from CMYK to both grayscale profiles of from this 2 grayscale profiles to RGB or other profile, you'll get exactly the same numbers except in the very highlights (below 5%) just because decimal conversions.

You're assuming "Black Ink - CGATS21_CRPC6.icc" came from the Black channel of CGATS21_CRPC6.icc what it's essentially not true. "Black Ink - CGATS21_CRPC6.icc" is just a synthetic ICC profile (not based on measurements) with a 20% dot gain and a different white points regarding the Adobe one.

Best regards.

------------------------------
Juan Martorell Climent
ColorInLab Color Consulting S.L.
Villarreal Spain
+34 964 523 278
------------------------------

Original Message:
Sent: 08-26-2019 02:50 PM
From: Brett Stone
Subject: Color Settings for Adobe Apps: Should Grayscale profile match CMYK profile?

I'm a content creator tasked with establishing color profile settings for my employer, as relates to all Adobe CC apps. We regularly provide print-ready PDF to a variety of print providers, including offset, flexo, and digital hybrid.
I've chosen Adobe RGB for our created print-ready RGB images, and selected GRACoL2013-C1 (CGATS21-2 CRPC6) for CMYK.
My question has to do with the setting for grayscale.
The various standard profiles (for example North America General Purpose 2) provided indicate Black default as 20% Dot Gain, and the same for Spot colors.
Wouldn't I want to set my Black profile to match the cmyk profile (in this case it would display as "Black Ink - CGATS21_CRPC6.idd in Photoshop Color Settings) so that this color behaves the same throughout the remainder of the production process?  [See attached screen cap for these settings]
In other words, if the black channel in a cmyk image is 50% tint (which passes through into my PDF) wouldn't I want my 50% gray tinted graphic to carry the same profile?
I can understand spot colors playing by the 20% dot gain rule, as those colors could be controlled on press independent of the cmyk. But the black channel is ultimately shared by both cmyk and grayscale images, and when we have cmyk images we are also likely to have gray images in the document, too. Shouldn't their profile settings match?
I'm fully open the idea that I'm thinking too hard about this, but I do want to get it right and not just by flipping a coin for each setting.
Thank you for your input -- it is valued and appreciated. ​​

------------------------------
Brett Stone
Owner
Yfficient Graphic Design and Marketing
Saint Charles MO
------------------------------

Brett,

------------------------------
Don Hutcheson
HutchColor, LLC
Washington NJ
908-500-0341
don@...
------------------------------

Original Message:
Sent: 08-27-2019 05:26 AM
From: Juan Martorell Climent
Subject: Color Settings for Adobe Apps: Should Grayscale profile match CMYK profile?

You're 100% correct as Don points you but.... you can forget about it. If you look internally to "Black Ink - CGATS21_CRPC6.icc" and to "Dot Gain 20%.icc" you'll see both are "identical" profiles (except by a little difference I'll mention later on). You can compare them just in PhotoShop (loading them in Gray ColorSpace and then looking to the curve going to custom) or in a match easy way just opening both profiles in ColorSync utility (in a Mac) or with ICC Profile Inspector in a PC. You'll see the KTRC curve (this is a GrayScale profile so it doesn't contain A2B or B2A tables, only curves) is the same one. Ok, you'll note it's starting in a different point (DG 20% starts in x,y 0,0 while Black Ink from CGATS21 starts in x,y 0,2.4) but this is because also the White Point in both profiles is set in a different way and even more this will be only considered if you use Absolute Colorimetric RI.

So basically if you convert from CMYK to both grayscale profiles of from this 2 grayscale profiles to RGB or other profile, you'll get exactly the same numbers except in the very highlights (below 5%) just because decimal conversions.

You're assuming "Black Ink - CGATS21_CRPC6.icc" came from the Black channel of CGATS21_CRPC6.icc what it's essentially not true. "Black Ink - CGATS21_CRPC6.icc" is just a synthetic ICC profile (not based on measurements) with a 20% dot gain and a different white points regarding the Adobe one.

Best regards.

------------------------------
Juan Martorell Climent
ColorInLab Color Consulting S.L.
Villarreal Spain
+34 964 523 278

Original Message:
Sent: 08-26-2019 02:50 PM
From: Brett Stone
Subject: Color Settings for Adobe Apps: Should Grayscale profile match CMYK profile?

I'm a content creator tasked with establishing color profile settings for my employer, as relates to all Adobe CC apps. We regularly provide print-ready PDF to a variety of print providers, including offset, flexo, and digital hybrid.
I've chosen Adobe RGB for our created print-ready RGB images, and selected GRACoL2013-C1 (CGATS21-2 CRPC6) for CMYK.
My question has to do with the setting for grayscale.
The various standard profiles (for example North America General Purpose 2) provided indicate Black default as 20% Dot Gain, and the same for Spot colors.
Wouldn't I want to set my Black profile to match the cmyk profile (in this case it would display as "Black Ink - CGATS21_CRPC6.idd in Photoshop Color Settings) so that this color behaves the same throughout the remainder of the production process?  [See attached screen cap for these settings]
In other words, if the black channel in a cmyk image is 50% tint (which passes through into my PDF) wouldn't I want my 50% gray tinted graphic to carry the same profile?
I can understand spot colors playing by the 20% dot gain rule, as those colors could be controlled on press independent of the cmyk. But the black channel is ultimately shared by both cmyk and grayscale images, and when we have cmyk images we are also likely to have gray images in the document, too. Shouldn't their profile settings match?
I'm fully open the idea that I'm thinking too hard about this, but I do want to get it right and not just by flipping a coin for each setting.
Thank you for your input -- it is valued and appreciated. ​​

------------------------------
Brett Stone
Owner
Yfficient Graphic Design and Marketing
Saint Charles MO
------------------------------

Hi Don.

This becomes an interesting issue :))

I'm trying to see and get this differences you mention, but honestly I'm not able to see them....

I believe the issue is in your PhotoShop settings. Let me proof you.

Instead of following your steps, do the process as I'll describe it right now.

1) Open the Lab_ramp.tif.
2) Add some color sampler tools into it, so you'll have point values.
3) Duplicate the image so you'll have two Lab images with color samplers in exactly same locations.
4) Convert the first one to Black Ink - CGATS21_CRPC6.icc" (Relative BPC as your suggestion).
5) Convert the second one to "Dot Gain 20%.icc" with the same settings (Relative BPC as your suggestion).
6) As you'll be now on Grayscale in both images, Photoshop rounds values in 8 bits to %, so for getting away of rounding issues, lets convert both images in RGB (AdobeRGB for example), so you'll get really round numbers and not an interpolated %.
7) take a look to the values and tell me if you found any difference between them. :))) (maybe you'll found differenced by 1 just because the calculations).

Now arrives a possible explanation of why you're getting this differences if you do the process following your steps. When you "copy" one of the images into the other one (point 3 of your process), by dragging one layer from one image into the other, depending on your color settings, the values of the channel will be converted or not, from one profile to the other one...

However this will have no sense for me knowing your deep knowledge about this topics, so maybe I'll be missing something. Any idea of why I'm not getting differences if I follow the previously steps? (or even following your steps and ensuring correct color setting in PhotoSop).

Best regards.






------------------------------
Juan Martorell Climent
ColorInLab Color Consulting S.L.
Villarreal Spain
+34 964 523 278
------------------------------

Original Message:
Sent: 08-27-2019 08:16 AM
From: Donald Hutcheson
Subject: Color Settings for Adobe Apps: Should Grayscale profile match CMYK profile?

Brett,

I hate to disagree with Juan, but there is in fact a considerable difference between converting to Dot Gain 20% and Black Ink CRPC6.

Juan, I'm surprised that a man of your intelligence, wisdom, good looks, charm (etc.) would make such a mistake! :-)

When you select an actual ICC profile as the Gray working space, Photoshop uses its "forward tag" (A2B) data to construct a 1-D LUT that converts from 0-100% K to L*. This becomes the forward tag of the Gray profile.
Photoshop then inverts that table to create the "reverse tag".
Note that this is NOT the same as just using the black channel of the profile as an output conversion, because obviously, the resulting tone shape would then be influenced by profiling software settings used when making the original profile, like Black start, Max black, Black shape, etc.

You can clearly see the difference as follows:

1. Convert a copy of my "Lab_ramp.tif" image (www.hutchcolor.com/Images_and_targets.html) into Dot Gain 20%, Relative, BPC.
2. Convert another copy into "Black Ink CRPC6", Relative BPC.
3. In the Layers window of one of the resulting K-only images highlight the Background layer and shift-drag it onto the other image. The shift key should make them register perfectly.
4. With the eye-dropper, create locked measuring points on patches that produced 100, 75, 50, 25 and 0% K.
5. Alternately reveal and hide the top layer (by clicking its eyeball icon) and watch as the percentages change.

You will see that the intermediate percentages (75, 50, 25, etc.) are significantly different, and shadow detail is also quite different.

This is one of Photoshop's hidden gems, that allows a 1-channel, black-only, reproduction to almost exactly match the tonality of a CMYK reproduction made for the same device. The only difference should be in deep shadows, which will usually have more contrast with four inks than just black.

Don

------------------------------
Don Hutcheson
HutchColor, LLC
Washington NJ
908-500-0341
<maskemail>don@...</maskemail>

Original Message:
Sent: 08-27-2019 05:26 AM
From: Juan Martorell Climent
Subject: Color Settings for Adobe Apps: Should Grayscale profile match CMYK profile?

You're 100% correct as Don points you but.... you can forget about it. If you look internally to "Black Ink - CGATS21_CRPC6.icc" and to "Dot Gain 20%.icc" you'll see both are "identical" profiles (except by a little difference I'll mention later on). You can compare them just in PhotoShop (loading them in Gray ColorSpace and then looking to the curve going to custom) or in a match easy way just opening both profiles in ColorSync utility (in a Mac) or with ICC Profile Inspector in a PC. You'll see the KTRC curve (this is a GrayScale profile so it doesn't contain A2B or B2A tables, only curves) is the same one. Ok, you'll note it's starting in a different point (DG 20% starts in x,y 0,0 while Black Ink from CGATS21 starts in x,y 0,2.4) but this is because also the White Point in both profiles is set in a different way and even more this will be only considered if you use Absolute Colorimetric RI.

So basically if you convert from CMYK to both grayscale profiles of from this 2 grayscale profiles to RGB or other profile, you'll get exactly the same numbers except in the very highlights (below 5%) just because decimal conversions.

You're assuming "Black Ink - CGATS21_CRPC6.icc" came from the Black channel of CGATS21_CRPC6.icc what it's essentially not true. "Black Ink - CGATS21_CRPC6.icc" is just a synthetic ICC profile (not based on measurements) with a 20% dot gain and a different white points regarding the Adobe one.

Best regards.

------------------------------
Juan Martorell Climent
ColorInLab Color Consulting S.L.
Villarreal Spain
+34 964 523 278

Original Message:
Sent: 08-26-2019 02:50 PM
From: Brett Stone
Subject: Color Settings for Adobe Apps: Should Grayscale profile match CMYK profile?

I'm a content creator tasked with establishing color profile settings for my employer, as relates to all Adobe CC apps. We regularly provide print-ready PDF to a variety of print providers, including offset, flexo, and digital hybrid.
I've chosen Adobe RGB for our created print-ready RGB images, and selected GRACoL2013-C1 (CGATS21-2 CRPC6) for CMYK.
My question has to do with the setting for grayscale.
The various standard profiles (for example North America General Purpose 2) provided indicate Black default as 20% Dot Gain, and the same for Spot colors.
Wouldn't I want to set my Black profile to match the cmyk profile (in this case it would display as "Black Ink - CGATS21_CRPC6.idd in Photoshop Color Settings) so that this color behaves the same throughout the remainder of the production process?  [See attached screen cap for these settings]
In other words, if the black channel in a cmyk image is 50% tint (which passes through into my PDF) wouldn't I want my 50% gray tinted graphic to carry the same profile?
I can understand spot colors playing by the 20% dot gain rule, as those colors could be controlled on press independent of the cmyk. But the black channel is ultimately shared by both cmyk and grayscale images, and when we have cmyk images we are also likely to have gray images in the document, too. Shouldn't their profile settings match?
I'm fully open the idea that I'm thinking too hard about this, but I do want to get it right and not just by flipping a coin for each setting.
Thank you for your input -- it is valued and appreciated. ​​

------------------------------
Brett Stone
Owner
Yfficient Graphic Design and Marketing
Saint Charles MO
------------------------------

Original Message------

Hi Don.

This becomes an interesting issue :))

I'm trying to see and get this differences you mention, but honestly I'm not able to see them....

I believe the issue is in your PhotoShop settings. Let me proof you.

Instead of following your steps, do the process as I'll describe it right now.

1) Open the Lab_ramp.tif.
2) Add some color sampler tools into it, so you'll have point values.
3) Duplicate the image so you'll have two Lab images with color samplers in exactly same locations.
4) Convert the first one to Black Ink - CGATS21_CRPC6.icc" (Relative BPC as your suggestion).
5) Convert the second one to "Dot Gain 20%.icc" with the same settings (Relative BPC as your suggestion).
6) As you'll be now on Grayscale in both images, Photoshop rounds values in 8 bits to %, so for getting away of rounding issues, lets convert both images in RGB (AdobeRGB for example), so you'll get really round numbers and not an interpolated %.
7) take a look to the values and tell me if you found any difference between them. :))) (maybe you'll found differenced by 1 just because the calculations).

Now arrives a possible explanation of why you're getting this differences if you do the process following your steps. When you "copy" one of the images into the other one (point 3 of your process), by dragging one layer from one image into the other, depending on your color settings, the values of the channel will be converted or not, from one profile to the other one...

However this will have no sense for me knowing your deep knowledge about this topics, so maybe I'll be missing something. Any idea of why I'm not getting differences if I follow the previously steps? (or even following your steps and ensuring correct color setting in PhotoSop).

Best regards.






------------------------------
Juan Martorell Climent
ColorInLab Color Consulting S.L.
Villarreal Spain
+34 964 523 278
------------------------------

Don and Juan,
I'm enjoying this conversation on my behalf, and I want you to both know that your input is greatly appreciated. Please stay friends! 
From the demo that Don just posted, I'm seeing that the blacks remain blacker (is that a thing?!) and the tonal range more complete. As a designer, I've often wondered why it was so difficult to achieve a deep black in gray images, and the DG20 may be a contributing factor (We also set our max % to 95%, which may be an unnecessary printer recommendation holdover from 'the old days', and the topic of a different conversation -- I've always wondered why I wouldn't provide the file with full tonal range and the printer adjust for press and paper realities in their process.)
I welcome additional conversation, whether it's Don, or Juan, or anyone else who would like to chime in. I'm learning much simply from everyone's input.

------------------------------
Brett Stone
Owner
Yfficient Graphic Design and Marketing
Saint Charles MO
------------------------------

Original Message:
Sent: 08-27-2019 12:19 PM
From: Donald Hutcheson
Subject: Color Settings for Adobe Apps: Should Grayscale profile match CMYK profile?

Hi Juan,

As you correctly assumed, when I dragged one image onto the other, I did NOT convert, so the K percentages were preserved.  The appearance of both layers was therefore controlled by the assigned profile of the receiving image.

Here is the difference I saw after converting into 20% Dot Gain (lower had) and Black Ink CRPC6 (top half).

I layered the 20% Dot Gain file over the Black Ink CRPC6 file and made a mask to show the difference at the dividing line. The difference is most visible in shadows.

Your suggested experiment:

Regarding your suggestion of converting both files to Adobe RGB, of course it seems to show no difference, because the test is fundamentally flawed.  (It's also unnecessary, BTW.)

Why it's flawed:

Converting the two K-only files to AdobeRGB (or any destination space) should ideally result in virtually identical appearance, because in both cases, the assigned profile should (hopefully) allow a colorimetrically-accurate translation back to the original Lab condition, as it existed prior to each file's conversion.

However what we want to know in this case is how would the K-only percentages appear when printed on a common destination device. Those differences are irretrievably lost when you convert into a second color space.

Why it's unnecessary:

You can see fractional percentages values simply by changing the eyedropper mode in the Info palette from 8 bit to 32 bit. The numbers are now expressed from 0.000 to 1.000, with three digits of precision.  Here's what it looks like...

The only slight annoyance is that now everything is inverted (100% = 0.000, 0% =1.000, but at least you have ten times the precision.

Does this help?

Don

**************************

Don Hutcheson

President

HutchColor, LLC

908-500-0341

<maskemail>don@...</maskemail>

**************************

Original Message------

Hi Don.

This becomes an interesting issue :))

I'm trying to see and get this differences you mention, but honestly I'm not able to see them....

I believe the issue is in your PhotoShop settings. Let me proof you.

Instead of following your steps, do the process as I'll describe it right now.

1) Open the Lab_ramp.tif.
2) Add some color sampler tools into it, so you'll have point values.
3) Duplicate the image so you'll have two Lab images with color samplers in exactly same locations.
4) Convert the first one to Black Ink - CGATS21_CRPC6.icc" (Relative BPC as your suggestion).
5) Convert the second one to "Dot Gain 20%.icc" with the same settings (Relative BPC as your suggestion).
6) As you'll be now on Grayscale in both images, Photoshop rounds values in 8 bits to %, so for getting away of rounding issues, lets convert both images in RGB (AdobeRGB for example), so you'll get really round numbers and not an interpolated %.
7) take a look to the values and tell me if you found any difference between them. :))) (maybe you'll found differenced by 1 just because the calculations).

Now arrives a possible explanation of why you're getting this differences if you do the process following your steps. When you "copy" one of the images into the other one (point 3 of your process), by dragging one layer from one image into the other, depending on your color settings, the values of the channel will be converted or not, from one profile to the other one...

However this will have no sense for me knowing your deep knowledge about this topics, so maybe I'll be missing something. Any idea of why I'm not getting differences if I follow the previously steps? (or even following your steps and ensuring correct color setting in PhotoSop).

Best regards.






------------------------------
Juan Martorell Climent
ColorInLab Color Consulting S.L.
Villarreal Spain
+34 964 523 278
------------------------------

Hi Don.

Now I see what you're talking about. I didn't realize of it as I was setting all color samples in the mid tones & highlights, and in this areas you can't see differences in color values. Now I've check initial Lab 5,0,0 and it's finishing in 98% in "Black Ink - CGATS21_CRPC6.icc" and in 95% in "Dot Gain 20%.icc", so 3% in difference in this dark areas.... yes, it's mathematically different... but I'm not sure if it'll be visible in a print.

On the other hand, you're absolutely right regarding the Adobe RGB conversion, I don't know in what I was thinking when I wrote it...maybe Jetlag...

What I initially was trying to explain Brett was the "Black Ink - CGATS21_CRPC6.icc" is not an ICC created from the black measurements of CGATS21_CRPC6.icc. If you convert the same Lab 5,0,0 into "CGATS21_CRPC6.icc", you can check the black channel finish in 91%. Of course you've the gray area coming from CMY that will increase the amount of gray in this area... but if you extract the just the black measurements from the CGATS of CGATS21_CRPC6.txt and build an output ICC (and convert this ICC from 1CLR to GRAY of course), so if you build a true ICC from the measurements, you can check it's absolutely different from "Black Ink - CGATS21_CRPC6.icc" as "Black Ink - CGATS21_CRPC6.icc" is a synthetic profile, not a profile from measurements as CGATS21_CRPC6.icc". In fact if you do it you'll see this Lab 5,0,0 is finishing on K=100%.

Brett. Don & me are and will be forever good friends, but both of us loves color and are passionated about it, so if there is something about what to get deep into, both loves to do it even just for fun... :)) Today I was recovering myself from a long trip and I had time for reading this forum.... so I was just enjoying a little discussing about something I like.

Best regards.

------------------------------
Juan Martorell Climent
ColorInLab Color Consulting S.L.
Villarreal Spain
+34 964 523 278
------------------------------

Original Message:
Sent: 08-27-2019 12:19 PM
From: Donald Hutcheson
Subject: Color Settings for Adobe Apps: Should Grayscale profile match CMYK profile?

Hi Juan,

As you correctly assumed, when I dragged one image onto the other, I did NOT convert, so the K percentages were preserved.  The appearance of both layers was therefore controlled by the assigned profile of the receiving image.

Here is the difference I saw after converting into 20% Dot Gain (lower had) and Black Ink CRPC6 (top half).

I layered the 20% Dot Gain file over the Black Ink CRPC6 file and made a mask to show the difference at the dividing line. The difference is most visible in shadows.

Your suggested experiment:

Regarding your suggestion of converting both files to Adobe RGB, of course it seems to show no difference, because the test is fundamentally flawed.  (It's also unnecessary, BTW.)

Why it's flawed:

Converting the two K-only files to AdobeRGB (or any destination space) should ideally result in virtually identical appearance, because in both cases, the assigned profile should (hopefully) allow a colorimetrically-accurate translation back to the original Lab condition, as it existed prior to each file's conversion.

However what we want to know in this case is how would the K-only percentages appear when printed on a common destination device. Those differences are irretrievably lost when you convert into a second color space.

Why it's unnecessary:

You can see fractional percentages values simply by changing the eyedropper mode in the Info palette from 8 bit to 32 bit. The numbers are now expressed from 0.000 to 1.000, with three digits of precision.  Here's what it looks like...

The only slight annoyance is that now everything is inverted (100% = 0.000, 0% =1.000, but at least you have ten times the precision.

Does this help?

Don

**************************

Don Hutcheson

President

HutchColor, LLC

908-500-0341

<maskemail>don@...</maskemail>

**************************

Original Message------

Hi Don.

This becomes an interesting issue :))

I'm trying to see and get this differences you mention, but honestly I'm not able to see them....

I believe the issue is in your PhotoShop settings. Let me proof you.

Instead of following your steps, do the process as I'll describe it right now.

1) Open the Lab_ramp.tif.
2) Add some color sampler tools into it, so you'll have point values.
3) Duplicate the image so you'll have two Lab images with color samplers in exactly same locations.
4) Convert the first one to Black Ink - CGATS21_CRPC6.icc" (Relative BPC as your suggestion).
5) Convert the second one to "Dot Gain 20%.icc" with the same settings (Relative BPC as your suggestion).
6) As you'll be now on Grayscale in both images, Photoshop rounds values in 8 bits to %, so for getting away of rounding issues, lets convert both images in RGB (AdobeRGB for example), so you'll get really round numbers and not an interpolated %.
7) take a look to the values and tell me if you found any difference between them. :))) (maybe you'll found differenced by 1 just because the calculations).

Now arrives a possible explanation of why you're getting this differences if you do the process following your steps. When you "copy" one of the images into the other one (point 3 of your process), by dragging one layer from one image into the other, depending on your color settings, the values of the channel will be converted or not, from one profile to the other one...

However this will have no sense for me knowing your deep knowledge about this topics, so maybe I'll be missing something. Any idea of why I'm not getting differences if I follow the previously steps? (or even following your steps and ensuring correct color setting in PhotoSop).

Best regards.






------------------------------
Juan Martorell Climent
ColorInLab Color Consulting S.L.
Villarreal Spain
+34 964 523 278
------------------------------