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Author Topic: Color space/bit depth in ACR  (Read 9989 times)
AFairley
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« on: February 24, 2010, 01:12:04 PM »
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I read the following statement about Lightroom:  

ALL editing is Lightroom is always 16bit per component in the ProPhoto RGB color space, regardless of the original file's colorspace. That's the working colorspace, and it is not changeable. Since ProPhoto RGB is a proper superset of all other colorspaces, this is a lossless transformation.

Is that what happens in ACR, and the bit depth and color space settings that are indicated on the clickable link underneath the preview window applied only upon export to file or opening in Photoshop, or is the image converted to the selected color space/bit depth on import to ACR?  I would expect the former, but want to be sure which it is.

Are RAW files, JPEGs and TFFs treated the same way?  

Thanks
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michael
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« Reply #1 on: February 24, 2010, 01:53:54 PM »
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Yes, and yes.

Think of 16 bit ProPhoto as a big mixing bucket into which your files are poured. When you work on them the bucket is big enough that nothing slops over and falls on the floor. When you then export it's up to you to decide what space they should be in depending on how they will be used.

Michael

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AFairley
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« Reply #2 on: February 24, 2010, 02:13:37 PM »
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Thanks Michael, appreciate the response.  I would have been very suprised if it was otherwise.
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Schewe
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« Reply #3 on: February 24, 2010, 02:29:06 PM »
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Quote from: AFairley
ALL editing is Lightroom is always 16bit per component in the ProPhoto RGB color space, regardless of the original file's colorspace. That's the working colorspace, and it is not changeable. Since ProPhoto RGB is a proper superset of all other colorspaces, this is a lossless transformation.

To be precise, Camera Raw/Lightroom use it's own internal color space based on Pro Photo RGB color coordinates in a linear (1.0) gamma. So, to call it "Pro Photo RGB" is incorrect. And yes, it's a huge color space but it would also not be correct to call a transform from an existing color space into the ACR/LR color space lossless. It's not lossless, but it _IS_ optimal and any data losses would be very, very minimal.
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fredjeang
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« Reply #4 on: February 24, 2010, 03:16:08 PM »
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sorry for my ignorance, but I do not understand one point.
We have a super and safe space color to work with in 16bits, but then, wich monitor is able to
reproduce al this spectrum?  
So we work in a great color space but we can not see all of it, and hardly reproduce them either.    

If I understand something, the reason would be that working the file in ProPhoto RGB space, some colors that have been captured
by the camera may possibly be visible on screen, if for example onces wants to push a red.
Is that correct? Then, after pushing where you wanted, onces export in a color space that is compatible by the printer, or the web?

I do not get it.

Fred.
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Schewe
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« Reply #5 on: February 24, 2010, 06:20:46 PM »
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Quote from: fredjeang
sorry for my ignorance, but I do not understand one point.
We have a super and safe space color to work with in 16bits, but then, wich monitor is able to
reproduce al this spectrum?

No printers can print all of it either...but Pro Photo RGB (the real color space) is an ideal archive and master RGB color space because it's the ONLY color space that CAN contain all the colors your camera can capture in raw AND all the colors that recent prints can print.

For a long time, displays were limited to sRGB or less...then came displays capable of all of the Adobe RGB color space...

It used to be that ink jet printers couldn't print any colors outside of sRGB...now recent 10 & 12 color printers can print colors outside of even Adobe RGB...

So, the ONLY color space to future proof your images is Pro Photo RGB....and the ability to contain all the colors a camera can capture is also why Thomas Knoll chose the PP RGB color coordinates for Camera Raw and Lightroom.



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digitaldog
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« Reply #6 on: February 24, 2010, 07:36:01 PM »
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Quote from: fredjeang
So we work in a great color space but we can not see all of it, and hardly reproduce them either.  


If your final output is a display, that’s an issue. Based on what Jeff said in terms of the gamut of modern printers, you have a choice. Dumb down (reduce the gamut) so you can see, all the colors and be unable to print them, or not see those colors that are there, but use them when you output the color. Most of would rather have option #2.

FWIW, there’s a nice chunk of “colors” (quotes on purpose) defined in ProPhoto RGB that fall outside human vision. Some would say if you can’t see them, they are not colors but that’s another discussion.
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Andrew Rodney
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Eyeball
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« Reply #7 on: February 24, 2010, 08:17:18 PM »
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I use ACR, not Lightroom, and in ACR the colors DO change inside the ACR window depending on what colorspace is chosen.  I see this in the actual color as well as when the clipping indicators are turned on.  I just wanted to clarify that because I think one could get the impression from the dialogue above that NO change is made to the image for colorspace until the image is saved or moved to PS.

Is that the way Lightroom behaves also?
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digitaldog
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« Reply #8 on: February 24, 2010, 08:30:45 PM »
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Quote from: Eyeball
I use ACR, not Lightroom, and in ACR the colors DO change inside the ACR window depending on what colorspace is chosen.  I see this in the actual color as well as when the clipping indicators are turned on.  I just wanted to clarify that because I think one could get the impression from the dialogue above that NO change is made to the image for colorspace until the image is saved or moved to PS.

Is that the way Lightroom behaves also?

No because unlike ACR, you don’t define the encoding color space until you export (or open in Photoshop). The numbers and histogram are based on Melissa RGB, while in ACR, those numbers and histogram (and clipping of course) is based on what you select in the workflow options.

That said, I don’t recall seeing a change in color or tone of the image when toggling the various color space options in ACR. The numbers and histogram, yes indeed.
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Andrew Rodney
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Eyeball
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« Reply #9 on: February 24, 2010, 08:44:50 PM »
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Quote from: digitaldog
No because unlike ACR, you don’t define the encoding color space until you export (or open in Photoshop). The numbers and histogram are based on Melissa RGB, while in ACR, those numbers and histogram (and clipping of course) is based on what you select in the workflow options.

That said, I don’t recall seeing a change in color or tone of the image when toggling the various color space options in ACR. The numbers and histogram, yes indeed.


That's what I thought.  So the answer to one of the OP's original questions is "yes, there is some difference in colorspace handling between ACR and Lightroom."

And yes, the colors do change in ACR.  I double-checked before posting.  The degree to which the change is visible would likely depend on the extent of any clipping and the gamut of the monitor but it changes.  I would never attempt even a minor correction of the likes of Michael Reichmann, Jeff Schewe, and Andrew Rodney unless I had double-checked and verified.
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digitaldog
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« Reply #10 on: February 24, 2010, 08:47:15 PM »
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Quote from: Eyeball
And yes, the colors do change in ACR.  I double-checked before posting.

So did I and I can’t see it...

The processing color space is the same. The encoding color space might be the same, it might not. Lightroom actually provides more options (you only get four in ACR).
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Andrew Rodney
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Tim Lookingbill
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« Reply #11 on: February 24, 2010, 09:06:26 PM »
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If you have a wide gamut monitor and create certain intense cyans, yellows and oranges in ProPhotoRGB there will be a slight but noticeable shift converting to sRGB.

To see this create a 100% cyan fill in a new standard SWOP v2 CMYK document in Photoshop. Convert that to ProPhotoRGB, then convert to sRGB and watch the cyan gain a bit of magenta and lose intensity. Same thing happens to intense yellows and oranges. This is the most shift you'll ever see converting from ProPhotoRGB to sRGB. If you see something greater, then their something wrong under the hood somewhere or you're working on a low gamut laptop.
« Last Edit: February 24, 2010, 09:07:52 PM by tlooknbill » Logged
Eyeball
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« Reply #12 on: February 24, 2010, 09:19:44 PM »
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Quote from: tlooknbill
If you have a wide gamut monitor and create certain intense cyans, yellows and oranges in ProPhotoRGB there will be a slight but noticeable shift converting to sRGB.

I was looking at a shot I took of Monarch butterflies in Michoacan, Mexico, so I think we're on the same track.  I don't have a wide-gamut monitor but I had to zoom to 100% and look carefully to see the change.  At first I thought it was affecting the clipping indicators only.
« Last Edit: February 24, 2010, 09:21:54 PM by Eyeball » Logged
Schewe
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« Reply #13 on: February 25, 2010, 11:45:49 AM »
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Quote from: Eyeball
And yes, the colors do change in ACR.  I double-checked before posting.  The degree to which the change is visible would likely depend on the extent of any clipping and the gamut of the monitor but it changes.  I would never attempt even a minor correction of the likes of Michael Reichmann, Jeff Schewe, and Andrew Rodney unless I had double-checked and verified.


Only the preview and the RGB numbers change in the Camera Raw dialog...the image doesn't change till you actually render the image into Photoshop...otherwise while the raw image is open inside of ACR the underlying processing pipeline keeps the image in the exact same color space regardless of the Workflow Settings.

The last set before opening in Photoshop is a color space transform from the processed file in the ACR color space to the final output profile set in the Workflow Settings...
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Peter_DL
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« Reply #14 on: February 25, 2010, 03:02:15 PM »
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>>That said, I don’t recall seeing a change in color or tone of the image when toggling the various color space options in ACR. The numbers and histogram, yes indeed.<<
Quote from: digitaldog
So did I and I can’t see it...
Yes, it can happen, devinitively.
I'm seeing it with sunsets. Subtile though.

I think it's once changing to sRGB output
while 1.0 pRGB > monitor gamut > sRGB for the relevant colors.

Histogram changes once changing to sRGB output
and it seems that the Preview pathway changes as well.

Peter

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FranciscoDisilvestro
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« Reply #15 on: February 25, 2010, 07:45:18 PM »
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From my experience I also see changes in colors in ACR when I change color space from ProphotoRGB to sRGB. It happens in those areas that are out of gamut in sRGB. It is the same change in color as opening the image in PS in ProphotoRGB and then convert to sRGB

I´m using ACR 4.6, on Windows XP.
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Schewe
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« Reply #16 on: February 25, 2010, 08:05:14 PM »
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Quote from: FranciscoDisilvestro
From my experience I also see changes in colors in ACR when I change color space from ProphotoRGB to sRGB.

Again, what you are seeing is in effect, soft proofing of the final output color space...in point of fact you are NOT seeing the impact of the final output color space of the raw processing pipeline because that doesn't change regardless of the output space...you are only seeing the preview and RGB numbers of the final color space.
« Last Edit: February 25, 2010, 10:53:19 PM by Schewe » Logged
FranciscoDisilvestro
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« Reply #17 on: February 25, 2010, 08:11:05 PM »
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Thanks, It makes a lot of sense
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FranciscoDisilvestro
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« Reply #18 on: February 25, 2010, 09:22:09 PM »
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Thinking about it, If ACR does softproofing (which I'm sure after Schewe explanation), why would you think Adobe did not included it in Lightroom?
It seems to me that it is probably the only one thing missing in the LR print workflow.
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Schewe
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« Reply #19 on: February 25, 2010, 10:52:18 PM »
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Quote from: FranciscoDisilvestro
...why would you think Adobe did not included it in Lightroom?

To be accurate, it's soft proofing of one of 4 color spaces only...that's NOT the same as soft proofing to arbitrary output profiles...

Yes, I would like real soft proofing in Lightroom...it would save a lot of trips into Photoshop. But I do tend to go into Photoshop for a lot of the retouching chores I need to do so it's not a deal breaker for me.

The bottom line is if you want the best possible output, you'll need to be doing final image optimizing in Photoshop even if only for the last 5-10% of you final imaging...those people who keep harping on getting EVERYTHING in Lightroom fail to understand that Lightroom will NEVER completely replace Photoshop and it's foolish to expect or demand that...

Lightroom for parametric editing, Photoshop for pixel editing...use the right tool for the job at hand.
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