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The Critically Important Color and Gamma Calibration Article


This article will explain how to understand and work with Photoshop's Color Management System (CMS), including how to create a custom profile, how to create an ICC profile for a monitor, how to set Photoshop's CMS defaults, how to use the Color Settings dialog box, and much more. It is excerpted from Inside Photoshop CS, by Gary D. Bouton. (Sams, 2004, ISBN: 0672326442).

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By: Sams Publishing
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December 15, 2004
TABLE OF CONTENTS:
  1. · The Critically Important Color and Gamma Calibration Article
  2. · Understanding Photoshop's Color Management System (CMS)
  3. · International Color Consortium (ICC)
  4. · Translation, Please
  5. · Preparing to Create a Custom Profile
  6. · Install the Latest Drivers for Your Equipment
  7. · Setting Photoshop's Color Management Defaults
  8. · The Settings Drop-Down List
  9. · Choosing from the RGB Working Spaces Drop-Down List
  10. · Color Management Policies
  11. · Conversion Options: Which Engine to Use
  12. · Black Point Compensation
  13. · Assigned Profile
  14. · Color Management Policies in Action
  15. · Converting a Profile Means Changing the Data
  16. · Soft-Proofing, or Seeing Onscreen What an Image Will Look Like When It's Printed

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The Critically Important Color and Gamma Calibration Article - Color Management Policies in Action
(Page 14 of 16 )

  1. Choose File, Open, and open Vision.tif from the Examples/Chap02 folder on the companion CD. This file has no profile attached, so a warning box should appear.

  2. In the Missing Profile dialog box that appears (see Figure 2.8), choose the Assign Working RGB: Adobe RGB (1998) option. Click OK to open Vision.tif.

Figure 2.8
The Missing Profile dialog box appears when you open files to which a color management profile is not attached. Use its options to assign a profile.


Insider - You could choose any working space by selecting one from the drop-down list, but because you don't know which working space this file was created in, and you haven't decided on a use for this file, the best choice is to assign Adobe RGB (1998). If you knew this file would be used for Web use only, choosing sRGB would also be okay. Remember—at this point you are deciding only how Photoshop should interpret and show the file to you; you have not changed any of the numerical data in the file.

If you had chosen the third option, Assign Profile, and picked from the pop-up list the same profile as the default working profile and checked the "and then convert the document to working RGB" option, you would have done two things at once. You would have set the interpretation of the data to Adobe RGB (1998) and changed the data (the word convert is the clue) to data that fits in Adobe RGB (1998) space. If you chose to assign some other profile, you would have made your view of the file that of the assigned profile, but with the option checked, the data would have been converted to the working space profile Adobe RGB (1998). It is usually not a good idea to create a mismatch when you open a file; doing so distorts your view and can lead to unexpected color shifts when the assigned profile is eventually matched to the data profile.


  1. Press Shift+Ctrl(Command)+S to open the Save As dialog box. Note that toward the bottom of the dialog box, in the section labeled Color, the option ICC Profile: Adobe RGB (1998) is checked (see Figure 2.9).


Insider - If you leave this option checked, the profile you assigned and noted here will be embedded in the file. This will become the profile that always governs your view of the file until you either assign a new profile or convert to another profile. If you remove the check from the profile, the file will not be color managed. Until you close the file, however, your view of the file will be from the perspective of the Adobe RGB (1998) profile.


Figure 2.9
The Color section of the Save As dialog box has options for embedding profiles in images.

  1. Find a place on your hard disk to save the file, and then click Save. In the TIFF Options dialog box under Image Compression, choose NONE, and choose the Byte order of your choice (PC or Macintosh). Do not check the Save Image Pyramid box. Click OK and leave the image open.

To recap, you've opened an image that did not have a color management profile attached to it and assigned a working profile to the file. You then embedded the profile in the file by saving the file to disk with the profile option checked. But how do you change the assigned profile for a file that already has a profile? In the next section, you'll seek out the rather obviously named Assign Profile command.

Changing the Assigned Profile

  1. With Vision.tif open in Photoshop's workspace, choose Image, Mode from the menu. Note at the top of the Image menu that RGB is checked. From this section of the menu, you could change the file to an entirely different color mode, like Grayscale or CMYK, but you can't change to a different RGB color space.

  2. Choose Assign Profile from the Image, Mode menu. In the Assign Profile dialog box that appears (see Figure 2.10), be sure the Preview option is checked. As you can see, this dialog box offers three choices: Don't Color Manage This Document, Working RGB: Adobe RGB (1998), and a Profile drop-down list that contains the standard RGB working spaces as well as every other RGB profile that has been made available to the CMS.


With the Preview option checked, you can see how different assigned profiles would look.

  1. Now let's see the effect on the document when we convert to a narrower color gamut such as CMYK. Click Cancel to close the dialog box without changing the Assigned profile. Go to the Image menu and choose Mode, CMYK Color. Notice that the colors in Vision.tif become duller: You've gone from a wide color gamut to a fairly narrow one, and the nuances of the Vision picture are being discarded. If you now choose Assign Profile from the Image, Mode menu, you will see that the Assigned profile in the dialog box is US Web Coated (SWOP) v2. This is what the file would look like in the editing window if you were to keep this profile. But remember, as long as you don't save these changes, you are changing only the interpretation, your view of the data, and not the data itself. (But this is what the data would look like if you did convert it.) Choose other profiles to see how they affect the view of Vision.tif. Then click Cancel to close the dialog box without changing the Assigned profile. Go to the File menu and choose Revert (to revert to the file settings when last saved). Again, notice the shift in colors as you return to the Adobe RGB (1998) color space. Leave Vision.tif open in the workspace.

Okay, let's say a client calls to say her company has decided it really wants to use the Vision.tif file on the Web, but that the company has decided not to use it for its print campaign. So you figure that now's the time to get this image prepped, and one of the first steps toward doing that is to move the file to the preferred color space of the Web, sRGB IEC61966-2.1. To move the file to that color space, you need to do more than simply change the assigned profile; you need to change the data in the file to ensure that all the colors in the image are within the smaller color space the Web uses. To change the data, you must convert the profile, and you'll see how to do that in the next set of steps.

This chapter is from Inside Photoshop CS,  by Gary D. Bouton. (Sams, 2004, ISBN:  0672326442). Check it out at your favorite bookstore today. Buy this book now.


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