Colour Management Policies

Colour Management Policies is a new phrase introduced by Adobe with Photoshop 6. The screen-grab below shows a typical setup, but this hides a lot of important information.

 

 

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. Also, don't be fooled by the fact that some of the choices have a direct equivalent in Photoshop 5, there are others that bear no relation, and for that reason, each needs to be viewed carefully.

The area zoned in blue in the above screen grab 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 really 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.

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 dialog will appear if Ask When Opening has not been activated for Profile Mismatches. 

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!

 

 

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.

(b) Preserve Embedded Profiles

For most situations this is my preferred choice of color 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 6 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, unless the user decides otherwise. 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, it is the case that the image preview is accurate.

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

 

 

When the image and the Working Space are matched then 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.

(c) Convert to Working Space

This policy behaves in an almost identical fashion to Photoshop 5. It's for this reason that many tend to favour it and in reality, it isn't a bad choice.

By default, if an image with no embedded profile is opened into Photoshop then the current Working Space will be used for editing and previewing, however, upon saving the image no profile will be embedded.

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 6 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 (via a scanner) 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.

 

 

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

I think you will agree that the above dialog is lot more user friendly than the one that appeared under similar circumstances when Ask When Opening was "unchecked".

(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 like the following and again contains three options; the pre-set selection is dependent upon the Colour Management Policy in operation at the time.

 

 

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 which does not embed a profile in the image file. 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 screen grab below shows the "Paste Profile Mismatch" dialog that will appear in the event of the color spaces of the two images not matching.

 

 

Note that the terms preserve "color appearance" and "color 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 Color Settings dialog if the user chooses to activate the Advanced "checkbox". The screen grab below shows this section of the Color Settings dialog in its default configuration.

 

 

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.

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 on-line help files.

As I understand things, 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.

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. Also note that the issue of muddy blacks that used to occur with Photoshop 5 appear to have been resolved.

Use Dither (8-bit/channel images): as with Black Point Compensation this should be kept "checked". The description box at the bottom of the Color 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 Color Settings dialog if the user chooses to activate the Advanced "checkbox". The screen grab below shows this section of the Color Settings dialog in its default configuration.

 

 

An explanation on what each of these options do is provided in the "Description" box and on-line help files. The consensus at present 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 cause the image on screen to become progressively less saturated as the percentage is increased. Those choosing to work in VERY wide colour spaces may find it useful, for the rest leave it "Off".

Finally, remember to 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 Color 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.

 

Customised Color Settings Configuration