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Colour Management Policies

Colour Management Policies was a new phrase introduced by Adobe with Photoshop 6 and continues virtually unchanged in Photoshop 7. The screenshot below shows a typical setup, but this hides a lot of important information.

 

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This section is probably the one that will cause most new Photoshop  users the greatest difficulty and for that reason the explanation that I give below will appear quite wordy, but don't be put off.

The area zoned in blue in the above screenshot is VERY important and I highly recommend that you make the same choices for Profile Mismatch and Missing Profiles as I have shown above. I usually refer to these particular selections as my "safety net", you'll see why shortly.

Basically each working space will have the same set of three options, although we need not configure each identically. These options are called Policies and include: -

(a) Off

In really simple terms, the "Off" Policy ensures that Photoshop does as little as possible when dealing with profiles. In most circumstances, it isn't a good choice and certainly not the choice to be made by new users. The following will give you some idea as to the default behaviour when this choice of policy is made.

  • Choosing "Off" will ensure that NEW images/documents will (by default) be saved without an embedded profile.
  • On opening an image with an embedded profile that matches the current working space, it will be retained and subsequently saved with the image.
  • The default Pasting behaviour between images is to retain numerical values (RGB pixel values), not the appearance. This means that no conversion between colour spaces will take place.
  • Opening an existing image that has an embedded profile that does not match the current working space (profile mismatch) will cause that embedded profile to be stripped out of the file. The image will subsequently be saved with no embedded profile. The following warning dialog will appear if Ask When Opening has not been activated for Profile Mismatches

 

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The problem with this configuration as compared to the one I recommended in the "Blue Zone" above is that the user either accepts what Photoshop dictates or doesn't open the image at all, not much of a choice. To me this choice is akin to the novice high wire walker operating without a "safety net", stay on the wire or fall off and break their neck! There are always exceptions-to-the-rule and I will later identify one that I find to be essential.

(b) Preserve Embedded Profiles

For most situations this is my preferred choice of colour management policy since it offers the greatest degree of flexibility, assuming the safety net mentioned above is in place. The following should give you an idea as to the default behaviour of Photoshop when this choice of policy is made.

  • Choosing "Preserve Embedded Profiles" will ensure that when an image is opened into Photoshop and is found to have an embedded profile that differs from the current Photoshop working space, then that image and its associated profile will be left intact. By default, Photoshop will make no attempt to convert the image to the current working space; the original embedded profile will be retained and subsequently saved with the image. Nevertheless, even though the image and Photoshop are no longer in sync, colour space wise, the image preview will be accurate.

 

  • When the image and the working space are matched Photoshop will take no action; the image is opened and saved as normal.
  • The default behaviour when Pasting either an RGB or Greyscale image is slightly more complex; whereby the appearance of the pasted image will be preserved but the numbers will change (the pixel values will change). In the case of CMYK it is the numbers that will be retained, not the appearance.
  • If the image being opened or imported has no embedded profile then Photoshop will use the current working space for editing and previewing purposes, however, the profile will NOT be embedded into the image when it is subsequently saved.
  • Creating a new document with this policy setting will mean that the current working space is used for editing, previewing and the associated profile will eventually be embedded into the file when saved.

The following dialog will appear if Ask When Opening has not been activated for Profile Mismatches. Again, my earlier comment about Photoshop imposing its will on proceedings applies.

 

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At first glance the above dialog appears virtually identical to that shown for the OFF Policy, but there is a subtle difference - the profile is retained rather than discarded.

(c) Convert to Working Space

This policy behaves in an almost identical fashion to Photoshop 5. It's for this reason that many still tend to favour it. Actually this policy isn't a bad choice but does need to be treated with care.

By default, if an image with no embedded profile is opened or imported into Photoshop then the current working space will be used for editing and previewing, however, upon saving the image no profile will be embedded. Photoshop will denote the image colour space as "Untagged RGB"

If an image is opened or imported and has an embedded profile which is found to differ from the current working space then that image will be converted into, and subsequently saved in the working space. When the image and the working space are matched then Photoshop takes no action; the image is opened and saved as normal. Newly created images will be edited, previewed and ultimately saved in the current working space.

Finally, the default pasting behaviour is to convert and thus preserve the appearance of the image. However, the user will get the option not to convert the pasted image, hence preserving the numbers if the pasted image doesn't match with the target image.

Overriding the Default Policy Behaviour

The previous section described how our choice of Colour Management Policy determined the default behaviour of Photoshop 7 under various scenarios. However, we need not be confined to these pre-set outcomes. At the beginning of the previous section I recommended that each of the "checkboxes" for Profile Mismatches and Missing Profiles be set for Ask When Opening or Ask When Pasting as appropriate. It is only through setting these checkboxes to "ON" that we can enable the default behaviour override facility. Furthermore, it is only by setting these checkboxes to "ON" that we can activate the "safety net".

Basically the three checkboxes have the following impact on the Colour Management Policies: -

(i) Profile Mismatches: Ask When Opening

Photoshop has been set to present the user with a dialog box when the image being opened or imported has an embedded profile that does NOT match the current working space. The dialog box looks like the following and contains three options; the pre-set selection is dependent upon the Colour Management Policy in operation at the time. Noticed that all the necessary information required to make an informed decision is present.

 

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The above example is pre-set for how the dialog would appear when the Colour Management Policy is set for Preserve Embedded Profile. The user may now choose to leave the image as is, allow the conversion or strip out the embedded profile and switch off colour management. Had the policy been Convert to Working Space  the dialog would have looked almost identical except that it would have been pre-set for "Convert document's colors to working space".

I think you will agree that the above dialog is a lot more user friendly than the one that appeared under similar circumstances when Ask When Opening was "unchecked". At least we now have the opportunity to assign an alternative profile to the image before it opens.

Warning!

Now that Photoshop can read the EXIF colour space information it's likely that many digital camera users will be seeing this particular dialog on a regular basis. Since no benefit will be gained by converting the image the best choice in such circumstances is to leave the default  "Use the Embedded Profile"  rather than be temped to choose "Convert document's colours to working space".

Users of cameras such as the Canon EOS 1D and Nikon D1X/H may have programmed the camera to process the images into the Adobe RGB (1998) colour space and will therefore know that the above warning is incorrect. In such circumstances they should choose to either accept the embedded profile or discard it, but they must then use the Assign Profile command to assign the correct profile. Both methods are equally valid. Remember Assign Profile does NOT change the image file only its appearance. Assign Profile and Convert to Profile are discussed on page 8.

If you have a custom profile for your digital camera you should follow the same workflow described for the 1D and D1X/H, but substitute your custom profile in for Adobe RGB (1998).

(ii) Missing Profiles: Ask When Opening

Photoshop has been set to present the user with a dialog box when the image being opened has no embedded profile. The dialog box looks similar to the following and again contains three options; the pre-set selection is dependent upon the Colour Management Policy in operation at the time.

 

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The above example is pre-set for how the dialog would appear when the Colour Management Policy is set for Preserve Embedded Profile. Since no profile is embedded Photoshop will try to assign the working space profile to the image. No conversion takes place, just the assignment of the working space profile.

The lower "Assign Profile (and the associated and then convert to working RGB)" checkbox is the best choice if you know the source images' true colour space and you want the image to appear in Photoshop. Typically, this option will be used for images from a digital camera or similar device that does not embed a profile in the image file or provide EXIF colour space information. Note that the source profile MUST be known and available to the user before this option can be selected.

(iii) Paste Profile Mismatches: Ask When Opening

The screenshot below shows the "Paste Profile Mismatch" dialog that will appear in the event of the colour spaces of the two images not matching.

 

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Note that the terms preserve "colour appearance" and "colour numbers" relate to the source image, not the destination.

The various dialogs that have been shown above are only a sample of those that may appear as you open or import images that contravene the defined Colour Management Policy. However, I think that the text messages included in each should be more than ample to explain what each option does and will therefore allow you to make the appropriate choice. 

Conversion Options

This section will only be present in the Colour Settings dialog if the user chooses to activate the Advanced "checkbox". The screen grab below shows this section of the Colour Settings dialog in its default configuration.

 

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Engine: this is the name of the engine, which will be used for all colour space conversions. Unless you have good reason to choose an alternative your should leave it at the default Adobe ACE setting. ACE is the direct equivalent of the Built-in engine used in Photoshop 5. Windows users should NOT be tempted to choose ICM. Mac users should keep in mind that the option chosen here will override the selection made in the ColorSync setup. Choosing the ColorSync engine is for Mac users as a bad a choice as Windows users choosing ICM

Intent: this pop-up menu allows the user to select from four different rendering intents, namely Perceptual, Saturation, Relative Colorimetric and Absolute Colorimetric. Typically, most users will choose between either the default Relative Colorimetric or Perceptual. A short description on each is provided in the Description section of the Color Settings dialog. A more comprehensive explanation can be found in the Photoshop on-line help files.

With Relative Colorimetric it is only those source colours that are out of gamut (i.e. can't be viewed/printed accurately within the destination colour space) that will be mapped to the closest in-gamut colour, the remainder are left unchanged. This means that in the case of images with lots of out-of-gamut colours the visual relationship between the colours (after conversion) will almost certainly change. With Perceptual, all colours of the source colour space will be mapped to the nearest in-gamut colour of the destination colour space thus maintaining the visual relationship between colours. In other words, with Perceptual the whole image colour gamut will be compressed so that it fits within the new colour space. The Photoshop default and recommendation is Relative Colorimetric and after considerable experimentation I have decided to go with Adobes recommendation.

Use Black Point Compensation: this should be kept "checked". Black Point Compensation ensures that the darkest neutrals of the source colour space are mapped to the darkest neutrals of the destination colour space. In most circumstances toggling BPC ON and OFF will result in no obvious change to the image appearance.

Use Dither (8-bit/channel images): as with Black Point Compensation this should be kept "checked". The description box at the bottom of the Colour Settings dialog box will give you some clue as to what it does.

Advanced Controls

As with the Conversion options, this section will only be present in the Colour Settings dialog if the user chooses to activate the Advanced "checkbox". The screenshot below shows this section of the Colour Settings dialog in its default configuration.

 

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An explanation on what each of these options do is provided in the "Description" box and on-line helps files. The consensus appears to be that both settings should be left in the default "Off" condition.

The Desaturate Monitor Color option is the one that has greatest potential to cause confusion as it will result in the image preview to become progressively less saturated as the percentage is increased. Those choosing to work in VERY wide colour spaces may find it useful, however, the majority of  Photoshop users should leave it "Off".

Saving Out Your Own Default Colour Settings

Select the Save button and give your settings a Name and Description by which you can call them back in the future, if for some reason you make a temporary change. Also note that you can have as many different sets of settings as you wish, although only one can be active at a time.

The screen grab below shows my own Colour Settings configuration. Notice that I have chosen Off for my Greyscale Policy and use a customised dot gain for the greyscale working space, you shouldn't try to repeat these settings since they are specific to my Piezography BW workflow.

 

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Customised Colour Settings Configuration

 

 

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