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Author Topic: Some questions about working with Absolute Colorimetric intents  (Read 5329 times)

BobDavid

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If you don't know what or why you'd use Absolute Colorimetric rendering intent, don't use it  ;D .

Absolute Colorimetric rendering intent is my preferred setting for printing scenes such as the one attached.  By the way, in deference to Mark Segal, I am retracting statements I made last October in re letting the printer (Epson P800) manage color. ... Photoshop is superior 99% of the time. Oddly, the first few images that I'd printed on the P800 had large patches of saturated blues and oranges (still barely within aRGB gamut). My unchecked enthusiasm resulted in a firestorm.

Seriously though, absolute colorimetric rendering intent, time and time again, is the better choice for the type of nighttime images I like to print. I typically make two master files: one for print, and the other for screen sRGB (with some additional tweaking). I use an Eizo for soft proofing and for inspecting sRGB conversions. Lastly, I check to see how the sRGB files appear on a current, but basic, Microsoft Surface Pro. The comparison is not dead-on, but it's reasonable.
 
The print of the shack photo is virtually identical to how it looks on both a Surface 3 and on a Surface Pro.
« Last Edit: May 10, 2018, 03:23:16 PM by BobDavid »
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digitaldog

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Absolute Colorimetric rendering intent is my preferred setting for printing scenes such as the one attached. 
The difference between it and RelCol only affects white. So what do you see differently doing that? The absolute colorimetric rendering intent reproduces the exact color that existed in the source—absolutely. If the source was light color on the dingy yellow-white of newsprint, the resulting color on your brilliant coated ink jet paper will be dingy yellow. This intent is really designed for making one device simulate the appearance of another device for use in proofing

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Andrew Rodney
Author “Color Management for Photographers"

BobDavid

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It allows for better detail in the shadows while still keeping the blacks nice and dark. Of course, I make a curve adjustment for the shadows and another one for the highlights. And depending on the media, I may add an additional curve for HSL.

I soft proof on a current entry-level Eizo Coloredge monitor. The white point is set at 4700K, which matches my Solux bulbs. I've found that 4700K is a good general purpose temperature. My monitor is placed in a controlled environment where the ambient light is dim and constant. The luminance of the monitor is 88 CDM.

Whether or not it's relevant, my workstation runs on Windows 7. I've not used an Apple since the late 1990s. My decision to migrate over to PC had more to do with practical business needs. ...not saying one platform is better than the other. I think both have strengths and weaknesses...
« Last Edit: May 10, 2018, 03:29:20 PM by BobDavid »
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BobDavid

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It's certainly possible that I could achieve comparable output using relative colorimetric intent. But from my experience using absolute colorimetric intent has greatly reduced the amount of time required in post. It's also streamlines the process of going from aRGB to sRGB for screen display.

I hope my description is clear.
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digitaldog

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It's certainly possible that I could achieve comparable output using relative colorimetric intent. But from my experience using absolute colorimetric intent has greatly reduced the amount of time required in post. It's also streamlines the process of going from aRGB to sRGB for screen display.

I hope my description is clear.
I see absolutely no difference converting from Adobe RGB (1998) to sRGB using Absolute or RelCol nor would I expect to see any difference. Nor do the numbers change between the two options. Can you explain what you mean?
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Andrew Rodney
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digitaldog

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It allows for better detail in the shadows while still keeping the blacks nice and dark.
Because there's no option for Black Point Compensation with Absolute. With RelCol you have the option to use it or not.

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Andrew Rodney
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BobDavid

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I see absolutely no difference converting from Adobe RGB (1998) to sRGB using Absolute or RelCol nor would I expect to see any difference. Nor do the numbers change between the two options. Can you explain what you mean?

I suppose I could take screenshots to demonstrate. As mentioned earlier, it's more about being a shortcut workaround in post than anything else.
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digitaldog

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I suppose I could take screenshots to demonstrate. As mentioned earlier, it's more about being a shortcut workaround in post than anything else.
Yes, you should!
Let me also help you with this example:
  • Open image in Adobe RGB (1998)
  • Duplicate it, name it Absolute
  • Convert one from Adobe RGB (1998) to sRGB using RelCol
  • Convert the other from Adobe RGB (1998) to sRGB using Absolute Colorimetric
  • Use Apply Image Command, subtract one from the other. Results below. THEY ARE IDENTICAL!
If you get something different, please supply the source document in Adobe RGB (1998). If you get the same results as I do, you fall into the camp of users who shouldn’t be using Absolute Colorimetric as I posted here!
« Last Edit: May 10, 2018, 03:53:58 PM by andrewrodney »
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Andrew Rodney
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Doug Gray

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Yes, you should!
Let me also help you with this example:
  • Open image in Adobe RGB (1998)
  • Duplicate it, name it Absolute
  • Convert one from Adobe RGB (1998) to sRGB using RelCol
  • Convert the other from Adobe RGB (1998) to sRGB using Absolute Colorimetric
  • Use Apply Image Command, subtract one from the other. Results below. THEY ARE IDENTICAL!
If you get something different, please supply the source document in Adobe RGB (1998). If you get the same results as I do, you fall into the camp of users who shouldn’t be using Absolute Colorimetric as I posted here!

Well, of course you are correct re converting Adobe RGB <> sRGB. There is a possibility David was thinking of something he did in the past like converting ProPhoto to either Adobe RGB or sRGB using the Microsoft ICM instead of Adobe's ACE. Big difference between those two.

But generally, stay away from Abs. Col. without good reason to use it. For instance if you print a gradient going from RGB 220,220,220 to 255,255,255 you will get clipping and likely a color shift as well  using Abs. Col. that you will not get with any of the other intents.
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digitaldog

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Well, of course you are correct re converting Adobe RGB <> sRGB. There is a possibility David was thinking of something he did in the past like converting ProPhoto to either Adobe RGB or sRGB using the Microsoft ICM instead of Adobe's ACE. Big difference between those two.
I have no idea what David is thinking, only what he wrote. I await his screen captures.
As for MS CMM vs. ACE, if there is a big difference, it’s a bug.
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Andrew Rodney
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Doug Gray

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I have no idea what David is thinking, only what he wrote. I await his screen captures.
As for MS CMM vs. ACE, if there is a big difference, it’s a bug.
It's a difference of interpretation of how media white points of D65 profiles (sRGB, Adobe RGB) are supposed to be mapped to/from D50 ones like ProPhoto. The ICC clarified it more than 15 years ago. Adobe follows the clarification. Microsoft doesn't. It is also a divergence between how CIE and the ICC defines "Absolute Colorimetric." There is a tech. note on it over at color.org.
« Last Edit: May 10, 2018, 04:51:58 PM by Doug Gray »
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digitaldog

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It's a difference of interpretation of how media white points of D65 profiles (sRGB, Adobe RGB) are supposed to be mapped to/from D50 ones like ProPhoto.
Yes. But again, in Photoshop, I see zero differences in how Absolute vs. RelCol convert from ProPhoto RGB let alone Adobe RGB (1998) with ACE. When I toggle to Apple CMM, the differences noted are absolutely awful appearing so I can't fathom why anyone would do so. Can you? And when the WP's are the same, as we see with Adobe RGB (1998)/sRGB, there's no difference with Apple's CMM. So until we hear back from David, I'm again at a loss to what or why he's doing what he reports he's doing. Maybe aRGB as he calls it, isn't Adobe RGB (1998); I wish people would use the proper names for these color spaces but that's another issue.
« Last Edit: May 10, 2018, 05:19:22 PM by andrewrodney »
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Andrew Rodney
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BobDavid

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Yes, you should!
Let me also help you with this example:
  • Open image in Adobe RGB (1998)
  • Duplicate it, name it Absolute
  • Convert one from Adobe RGB (1998) to sRGB using RelCol
  • Convert the other from Adobe RGB (1998) to sRGB using Absolute Colorimetric
  • Use Apply Image Command, subtract one from the other. Results below. THEY ARE IDENTICAL!
If you get something different, please supply the source document in Adobe RGB (1998). If you get the same results as I do, you fall into the camp of users who shouldn’t be using Absolute Colorimetric as I posted here!

Here are three screen shots: Absolute, Relative with Black Point Compensation, and Relative (soft proofs for Epson Ultra Premium Luster Photo Paper). Photos were taken with an Olympus Pen F in 8-shot mode for color fidelity and to control moire. The three RAW files were minimally processed as one batch with all adjustment in sync.
« Last Edit: May 10, 2018, 05:23:20 PM by BobDavid »
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digitaldog

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Here are three screen shots: Absolute, Relative with Black Point Compensation, and Relative (soft proofs for Epson Ultra Premium Luster Photo Paper).
A. I see no difference.
B. None are conversions you stated below (Adobe RGB (1998) or what you call aRGB to sRGB.
So exactly what are you referring to?
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Andrew Rodney
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BobDavid

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I see significant differences in the shadow detail of the trees in the sky and the luminance of the light projecting onto the street. The differences are clearly there, but being that you're looking at photos of a screen, the differences will not hit you in the face as much as what is visible to the naked eye when looking directly at the monitor.

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BobDavid

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A. I see no difference.
B. None are conversions you stated below (Adobe RGB (1998) or what you call aRGB to sRGB.
So exactly what are you referring to?

The pictures on the monitor are aRGB. I photographed the screens in aRGB, and then downsized and saved as jpgs (8-bit, sRGB).
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digitaldog

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I see significant differences in the shadow detail of the trees in the sky and the luminance of the light projecting onto the street. The differences are clearly there, but being that you're looking at photos of a screen, the differences will not hit you in the face as much as what is visible to the naked eye when looking directly at the monitor.
I can't see significant differences in your screen captures which BTW are untagged here.
Next and again, NEITHER is a conversion from the RGB working space you specifically referred to! Here's your exact text:
Quote
It's also streamlines the process of going from aRGB to sRGB for screen display.
Next and again, the differences between RelCol and Absolute, as you were told, is one allows Black Point Compensation while the other does not. Yet you have it ON in one screen capture but not the other. They have nothing to do with the quote above you made about aRGB (presumably Adobe RGB (1998)) and sRGB.
I'll ask again, what exactly are you referring to? 
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Andrew Rodney
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BobDavid

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Should be tagged. I exported as sRGB. I will post them again if you want.
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digitaldog

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Should be tagged. I exported as sRGB. I will post them again if you want.
I assigned sRGB. But that doesn’t explain what you wrote.
Is there going to be a difference going from any RGB working space to a print space using Absolute vs. RelCol? Sure. No one is disputing that. Is there a difference converting Adobe RGB (1998) to sRGB using either? No, there is NO difference. Begging the question again, what does this mean:
Quote
It's also streamlines the process of going from aRGB to sRGB for screen display.
Was this question unclear to you?

Quote
I see absolutely no difference converting from Adobe RGB (1998) to sRGB using Absolute or RelCol nor would I expect to see any difference. Nor do the numbers change between the two options. Can you explain what you mean?
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Andrew Rodney
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BobDavid

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I can't see significant differences in your screen captures which BTW are untagged here.
Next and again, NEITHER is a conversion from the RGB working space you specifically referred to! Here's your exact text: Next and again, the differences between RelCol and Absolute, as you were told, is one allows Black Point Compensation while the other does not. Yet you have it ON in one screen capture but not the other. They have nothing to do with the quote above you made about aRGB (presumably Adobe RGB (1998)) and sRGB.
I'll ask again, what exactly are you referring to?

The file is an aRGB file. The monitor is set in soft proof to show Absolute, Relative, and Relative with black point compensation. Forget about sRGB--I only brought that up because Chrome as of yet is not color managed while Firefox and Safari are. I use chrome.
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