ASSIGN Versus CONVERT to Profile
Photoshop Color Management
In my lay style for lay Mac users (like me)
© 2004 www.gballard.net Main Site

PHOTOSHOP — any color management system or application — cannot Display, Print or Convert a file accurately unless it knows the file's Source Space, a.k.a. source profile, ICC Profile, ColorSync profile, color space.

There are ONLY three ways Photoshop can possibly know a SourceFile's SourceSpace:

  1. The file is tagged with an embedded ICC profile, we HONOR the tag.
  2. We: Photoshop> Image> Mode> (or in CS2 Edit>) ASSIGN (the correct) Profile.
  3. The file's SourceSpace EQUALS Photoshop's WorkingSpace (by chance or by workflow).

This online Photoshop tutorial uses the CS3 PSCS2 CS1 PS10 PS9 PS8 PS7 PS6 Assign Profile Convert Profile features to explain how to honor embedded profiles and convert to target profiles through Adobe Photoshop color management theory.

The Basic Theory behind Photoshop Color Management gballard.net.

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1) We HONOR the Embedded Profile:

HONORING embedded profiles is NOT negotiable (if we are opening RGB or CMYK files in Photoshop)!
THE FACTS ARE if we ignore the embedded profile, we change (hose) the file the moment we open it...please read the link if you think ignoring or stripping embedded profiles or turning color management off are good ideas.

  • IF you are using a color-managed web browser, this color management test page will display the three PDI_Target files the same because the web browser is Honoring the embedded profiles (and Converting or correcting the color to your monitor profile for viewing).
  • IF your browser is not color managed, all three files there will look different (hosed) because the dumb application, the browser, is stripping the embedded profiles (and making incorrect Assumptions about the RGB). This is the exact problem Photoshop has when it is told to strip or ignore embedded profiles....

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2) We Photoshop> Image> Mode> (or Edit) ASSIGN (the correct) Profile:

There are ONLY two times we use ASSIGN Profile:

1) The file is Untagged (we must tell Photoshop the file's correct ColorSpace).

2) The file looks bad on a calibrated monitor (the file is mistagged, or balanced on an inaccurate monitor, we use Photoshop to look for a better ColorSpace, one that displays the file better on an accurate, calibrated monitor).

I like to think of this Assigning process as "fishing" around for the best ColorSpace to ASSIGN below.

As Bruce Fraser creativepro.com explained in an Adobe Forum (excerpted):

  • "If everyone played nice and embedded profiles so that we knew what colors the numbers were supposed to represent, Assign Profile would be either unnecessary or an expert feature for total geeks.
  • "I've seen more files wrecked by people opening perfectly good tagged files and either stripping the profile deliberately, having the software set up to discard the embedded profile, or using some antediluvian version of Photoshop that doesn't understand profiles, than from any other cause.
  • "If I ruled the world, Assign Profile would only be enabled for already-tagged files if the user correctly answered 100 or so fairly tough color management questions, and signed a waiver. It's fine for people who know what they're doing to experiment with Assign Profile, but it's really an expert feature...".

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3) Source Space EQUALS Working Space:

There is ONLY one way a file's SourceSpace can EQUAL Photoshop's WorkingSpace:

1) The file was last saved, tagged or untagged, in Photoshop's current WorkingSpace.

But to expand my "EQUAL" point.

Photoshop's Working Spaces are set in Photoshop> Edit> Color Settings:

In Photoshop 10 CS3 and CS2 PS9: set Photoshop Color Settings> Settings> to North American Prepress 2 now (for the tutorial).
Or in Photoshop CS1, PS8 7 6, set US Prepress Defaults.

With the above Color Settings, any RGB file we Save will be in the Adobe RGB (1998) ColorSpace (regardless if we embed a profile or don't embed a profile) the file is based on the AdobeRGB profile, ColorSpace, i.e., Working RGB.

NOTE: Unless, of course:
1) We Image> Mode> CONVERT to (a different) Profile before Saving, or
2) We opened a file outside of Photoshop's WorkingRGB (Adobe RGB) and did not Convert it to WorkingRGB.

Likewise, any CMYK file we Save will be in the US Web Coated (SWOP) v2 ColorSpace (regardless if we embed a profile or don't embed a profile) the file is based on the US Web Coated (SWOP) v2 profile, ColorSpace, i.e., Working CMYK.

NOTE: Unless, of course:
1) We Image> Mode> CONVERT to (a different) Profile before Saving, or
2) We opened a file outside of Photoshop's WorkingCMYK (US Web Coated (SWOP) v2) and did not Convert it to WorkingCMYK.

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My original HONOR, ASSIGN, EQUAL points are very easy to PROOF in Photoshop:
PDI Graphic
DOWNLOAD *iPhotoTESTfolder.sit (6MB) for Mac.
DOWNLOAD *iPhotoTESTfolder.zip (6MB) for PC.
*iPhotoTESTfolder contains a collection of six files of one image in various ColorSpaces, in tagged/untagged states, designed to PROOF how the different profiles, ColorSpaces, gammas react on screen.
• PDI_Target images are owned and Copyrighted by PhotoDisc gettyimages.com.
• PDI_Target DOWNLOAD files have been altered by G. BALLARD for this tutorial, in accordance with PhotoDisc's licensing terms. The unaltered PhotoDisc JPEG and License are included in DOWNLOAD.
These ColorSpaces may be PROOFed on the internet sRGB is the Correct ColorSpace for the Internet gballard.net.

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In this tutorial test:

1) Color Settings: Set Photoshop's Color Settings to US Prepress Defaults
Or in Photoshop CS3 PS 10 and CS2 PS9, set North American Prepress2.
(this sets WorkingRGB to equal Adobe RGB (1998) AND closes Photoshop's BackDoor gballard.net):

2) Open the three UnTagged iPHOTO Test files as noted:
UTadobe.jpg, UTapple.jpg, UTsrgb.jpg
At Missing Profile: "Leave as is (don't color manage)":

With all three Untagged files open, notice Photoshop is displaying only the Untagged AdobeRGB (UTadobe.jpg) file correctly because Photoshop is making the correct Assumption -- based on "WorkingRGB EQUALS AdobeRGB" -- and Photoshop is completely hosing the Untagged sRGB and AppleRGB because it made incorrect Assumptions (WorkingRGB does not equal AppleRGB/sRGB).

If we think about it, Photoshop displaying Untagged AdobeRGB correctly (over Untagged AppleRGB and sRGB, monitor-type profiles) seems completely illogical and drives home my point:

  • Adobe RGB (1998) gballard.net is a device independent ColorSpace -- it has nothing to do with monitor profiles.
  • AppleRGB and sRGB ColorSpaces are both based on monitor-type profiles.

At first thought, the logic would be -- if the files are Untagged -- Photoshop would display the monitor-type profiles correctly (and completely hose the device-independent AdobeRGB color). But in fact, the complete opposite is happening BECAUSE:

  • Photoshop ASSUMES Untagged files EQUAL its WorkingSpace (AdobeRGB), the Untagged AdobeRGB is being properly Converted to MonitorRGB.
  • Photoshop ASSUMES Untagged files EQUAL its WorkingSpace (AdobeRGB), the Untagged AppleRGB and sRGB are being incorrectly based on AdobeRGB and show the bad Conversion to MonitorRGB.

See Andrew Rodney gballard.net for more on HOW Photoshop CS deals with Untagged files and HOW Photoshop 4 and earlier deals with color.

3) Open the three Tagged iPHOTO Test files, as noted:
adobe.jpg, apple.jpg, srgb.jpg
At Embedded Profile Mismatch: "Use the embedded profile (instead of the working space)":

All three Tagged test files look identical to the Untagged AdobeRGB BECAUSE all three files are being correctly Converted into MonitorRGB -- Photoshop knows the Tagged Source Files' Source Spaces through their embedded profiles, and the Untagged AdobeRGB through SourceSpace EQUALS WorkingSpace.

See Bruce Fraser creativepro.com for more on using these Photoshop Color Management Policy splash screens....

4) Further: Image> Mode> (or Edit>) ASSIGN (AppleRGB) Profile to the Untagged AppleRGB file, and Image> Mode> (or Edit>) ASSIGN (sRGB) Profile to the Untagged sRGB:

Now ALL SIX FILES ARE DISPLAYING IDENTICAL because:

  1. We HONORED the embedded profile on the three tagged files.
  2. We Image> Mode> (or Edit>) ASSIGNED (the correct) Profiles to the Untagged AppleRGB and sRGB files.
  3. The Untagged AdobeRGB EQUALS Photoshop's WorkingRGB (AdobeRGB).

If I've done my journalistic and tutorial job correctly, my point should be coming obvious with a review and Further Practice...my core point should be crystal clear:

• Photoshop must know the Source File's Source Space (or it will change the file's color mapping and hose ALL Conversions).

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Further Practice:

Open any file in Photoshop:

  1. Image> Mode> Assign (sRGB) Profile
  2. Image> Mode> Assign (AdobeRGB) Profile
  3. Image> Mode> Assign (AppleRGB) Profile
  4. Image> Mode> Assign (MonitorRGB) Profile

Photoshop 9 CS2 changed the Assign menu -- now: PS> EDIT> ASSIGN PROFILE.

NOTICE THE FILE CHANGES because ASSIGN Profile tells Photoshop to re-define, to re-map, to re-base its Conversion to MonitorRGB, on different "numbers," different color "maps" (thereby changing, altering Photoshop's interpretation of the original SourceFile).

IN A GENERAL WORKING SENSE:
These color changes on screen - under ASSIGN Profile - effectively illustrate HOW, Assigning different profiles actually changes the file (by remapping, redefining the file's ColorSpace).

IN THE ACTUAL, FACTUAL, TECHNICAL SENSE:
Assigning different profiles - in fact - does NOT change the actual file, as Bruce Fraser so eloquently put it:

(You could change profiles a thousand times via Assign Profile and the image would not degrade) "Inasmuch as the numbers in the file wouldn't change, this is true. But it would display incorrectly, and convert to any other space incorrectly, so it's fair to say that while the integrity of the data hasn't been compromised, and you can rescue the file by assigning the correct profile, for all practical purposes, it's hosed," Bruce Fraser wrote in the Adobe Photoshop Forum.

BTW, in the above is "fishing" around for the best profile technique - Bruce Fraser's Mystery Meat analogy - we ASSIGN various profiles, ColorSpaces until we get the best color on a calibrated monitor, then Image> Mode> Convert to (desired) Profile.

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Not to trick you but :)

Open any Tagged file in Photoshop:

  1. Image> Mode> Convert to (sRGB) Profile
  2. Image> Mode> Convert to (AdobeRGB) Profile
  3. Image> Mode> Convert to (AppleRGB) Profile
  4. Image> Mode> Convert to (MonitorRGB) Profile

Photoshop 9 CS2 changed the Convert menu -- now: PS> EDIT> CONVERT TO PROFILE.

NOTICE THE FILE DOES not CHANGE because Photoshop knows the SourceSpace, and is merely CONVERTING the SourceSpace to a TargetSpace -- whilst all the time Converting the changing SourceSpace> MonitorRGB, on-the-fly, (so it is PROOFing the SourceSpace accurately on the monitor in real-time).

The fact that the color does not change on screen under CONVERT effectively illustrates HOW Converting SourceSpace profiles maintains the faithful color appearance even though the Source File's Color Space is changed, remapped, altered.

Conversions degrade color, so avoid Conversions until/unless necessary.

Keep in mind Image> Mode> Convert to Profile ALSO degrade color information.
For example, Converting an AdobeRGB file to sRGB "clips" significant color information.

I like to think of the clipping process as flattened cookie dough (of AdobeRGB color info).
The sRGB cookie cutter clips out the sRGB shape (to make the desired color shape), and the remaining dough (the unused information) is discarded (and irretrievable).

We can Convert (add a bigger shape around the clipped shape) back to a higher gamut, larger color space, but we gain no additional information (than what is left of the smallest clipped shape). In other words, all that is left between the clipped shape and the new shape is empty space.

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It may take some thinking and more reading to totally grasp these issues, but it is truly The Core Theory gballard.net behind Photoshop Color Management, and it is no more complicated than this:

MonitorRGB < SourceSpace > TargetSpace

On this page, we've only explored the SourceSpace> MonitorRGB Conversion side of the theory (which happens on-the-fly in real-time behind the scenes in Photoshop to PROOF the file accurately on screen) -- and -- the SourceSpace> SourceSpace Conversion (a move that actually changes the file).

The SourceSpace> Target(Device)Space Conversion -- to a SPECIFIC Printer/Paper/Ink profile for example -- works on this same principle....

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I like to explain Epson Photoshop ColorSync printing in a NoColorAdjustment WorkFlow gballard.net.

The main goal of digital color imaging is to CAPTURE as much color information as possible, and to PRESERVE that color information throughout the editing processes...see my Photoshop Adjustment-Layer Workflow gballatd.net.

Please check out my Main Site for additional lay Rants (and direct Resource Links to the very best expert writers on the internet).

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by: ©2004 G. BALLARD • www.gballard.net
Note: G. BALLARD prefers a shredding if he is wrong or unclear.

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