Section 4.2. Calibrate and Profile Devices


4.1. Establishing a Working Color Space

Choose a working color space that is optimized for your particular image-editing workflow. Which color space you use is less important than how you manage it. We'll start with simple color spaces. You can use a more advanced working color space once you are ready to move on to the next level.

4.1.1. Which One Do I Pick?

Here are five scenarios for choosing different working space setups in Photoshop:


sRGB: gamma 2.2, 6500K

Use only when sending files to a photographic lab that requires sRGB or when creating files for the Internet.


Adobe RGB (1998): gamma 2.2, 6500K

The most popular working color space. Use for ink-jet printing, prepress, and photographic labs.


Apple RGB: gamma 1.8, 5000K

Use for legacy Apple monitors; similar to sRGB.


ColorMatch RGB: gamma 1.8, 5000K

Use for prepress, preparing files for a printing press, or newsprint.


ProPhoto RGB: gamma 2.2, 6500K

The largest working color space. Encompasses an advanced color management workflow.

When choosing your working color space, it is best to consider your primary output. For instance, if your work is usually printed in-house on an ink-jet printer, Adobe RGB (1998) or ProPhoto RGB is a good choice. If you send files to a photographic lab, check with the lab to see if it has color space requirements, and if it does, use that color space as your working space. Note that you don't have to use the same space that the lab does; doing so can help in production, but it isn't completely necessary.

If you have an ink-jet workflow in addition to your photographic lab workflow, one option is to use Adobe RGB (1998) as your working space and convert to the lab's space when you're ready to send the file. At the end of this chapter, I'll show you how to establish an action to convert to sRGB and save in a folder ready for the lab.

NO SPACE LIKE HOME

There are three types of color spaces a file might have: an input profile (such as a scanner or digital camera profile), a working color space profile (such as ProPhoto RGB used during the image-editing phase), or no color space profile. I refer to a file's color space as a "home." So, when a file has a color space, it has a home, and when there is no color space embedded, it has no home. A color-managed workflow is much easier when a file has a color space home to start with.

If a file has no home (color space) these days, it is usually because it was created or scanned before color spaces were tagged in files. Or perhaps it has gone through a process where no ICC profile was included; for instance, it's gone through the Image Processor in Photoshop with the option "Include ICC Profile" (see the bottom of the screen) left unchecked. When this box is unchecked, the processed images are stripped of any home color space they started out with. Processing a file without an ICC profile is sometimes done for the Internet or when requested by an end user.


4.1.2. Setting Your Working Color Space

You can set your working color space in Photoshop under Edit Color Settings. This opens the Color Settings screen where you can select the RGB working space that is suited for your particular workflow. Photoshop is quite capable of managing any color space a file is tagged with, and even more impressive, Photoshop can handle multiple color spaces (from multiple open files) all at the same time.

At the top of the Color Settings window is a drop-down menu for choosing a set of overall Settings. (In this example, it's set to the default: North America General Purpose 2.) This setting gives you specific working spaces for each color model; in this case, sRGB IEC61966-2.1 is the default RGB Working Color space along with U.S. Web Coated SWOP v2 for CMYK and Dot Gain 20% for Gray and Spot.

You can set any of the items in the Working Spaces box independently. For RGB, there are four primary choices: Adobe RGB, Apple RGB, ColorMatch RGB, and sRGB. My personal choice for my working color space is Adobe RGB because my workflow includes processing images for ink-jet printing, photographic labs, and prepress, and this working space covers most of these output gamuts during conversion.

I do, however, embed ProPhoto RGB in all of my RAW files when I process them through Adobe Camera Raw in order to preserve the highest amount of pixel data for current and future use.


In the next box are the Color Management Policies options. The default setting for each color mode is to Preserve Embedded Profiles, which is the best choice when you work with images that have various embedded profiles. From each of these drop-down menus, you can also choose "Convert to Working RGB," which is a good choice when you have a closed loop workflow (such as shooting with one camera and printing to one printer) or if you are processing images for use on the Internet. "Convert to Working" RGB is designed to automatically convert files to your chosen working space according to the model (i.e., RGB, CMYK, Gray) when you open them in Photoshop. The Off option will pass the files straight through, but Photoshop may display a message when you open a file to remind you that the tagged file is different from your chosen RGB working space.

4.1.2.1. Mismatch warning

Checking the options for when Photoshop should ask you about Profile Mismatches and Missing Profiles will cause Photoshop to display a warning when you open images that are not in your working RGB color space. The warning will show you which profile is embedded and options to manage the document's profile. If a file has a color space home, keep it by selecting "Use the embedded profile"; that is the best policy unless the embedded profile is from an input profile such as a scanner or digital camera. In that case, choosing "Convert document's colors to the working space" will convert the color space into your color space workflow.

In a color-managed workflow, when a file has no embedded profile, you certainly want to assign one to it. Photoshop offers two choices for assigning a profile, and which one you choose depends on the source of the file. In most cases, the second choice, "Assign working RGB," is best. If you have a scanning or digital camera workflow but the device does not apply an input profile, choosing an "Assign profile" option from the pull-down menu allows you to select the scanner or digital camera profile that works best. You also have the option of then converting to your working RGB, which is the best choice in most cases.

Photoshop also offers one of these options: "Leave as is (don't color manage)" or "Discard the embedded profile (don't color manage)." These options are handy when you must process images with no profile embedded. If you have a file with a tagged profile but your lab requests an untagged image, from the main menu in Photoshop you can choose File Save As.... In the Save As dialog box, youll find an option at the bottom to uncheck Embed Color Profile. This will strip the embedded profile for your lab's requirements.

In creating screenshots for this book, I did not have embedded profiles. In this case, I chose "Assign profile," selected my calibrated monitor's profile, and then checked "and then convert document to working RGB." This funneled the color of the screenshot to maintain the proper color appearance. Using this technique also works very well for images you prepare for the Internet.


4.1.2.2. Advanced options

Click on the button to expand the Color Settings window. You now have Conversion Options, Advanced Controls, and if you select the RGB drop-down menu in Working Spaces, you'll notice a gazillion choices for a working space. (Here you can choose ProPhoto RGB as your working space, but select this profile only if you are an advanced user. )

In the Conversion Options box, you can set a couple of the items we learned about in Chapter 2. The default engine, Adobe (ACE), works very well when converting profiles in Photoshop. (The engine is the Color Management Module that we discussed in Chapter 2.) Adobe (ACE) is the best choice unless you have a specific reason for using a different engine. What you select for the other options will depend on your operating system and any other software you may have installed. Here you can also set your Rendering Intents (as we discussed in Chapter 2). Relative Colorimetric and Perceptual are the two most commonly used rendering intents. In a basic workflow, consider Relative Colorimetric for ink-jet printing and Perceptual for photographic paper printing, such as your lab might use.

Checking the Use Black Point Compensation options will compensate the black point of your image according to your (properly calibrated) monitor's profile. When the known values of a black point are displayed on your monitor, this option attempts to replicate this known black point. Using Dither (8 bit/channel images) will ease the transition between profiles where banding may become apparent. Both options should be checked.

With so many options to pick from, choosing the right ones can seem overwhelming to say the least. But establishing your working spaces and color management policies is of the utmost importance. With the exception of selecting sRGB as a working space in most cases, using the default settings on everything else works well and is recommended for a basic color settings setup.


In the Advanced Controls, you will find the option to Desaturate Monitor Colors by a specific percentage. This option is rarely used today, even though it does offer compensation for overly saturated monitors once a consistent workflow has been established. The Blend RGB Colors Using Gamma option is designed to dither your brush edge with certain color blendings, which may result in fewer edge artifacts.

In the Description box at the bottom, you'll find a wonderful amount of information regarding anything that your cursor hovers over. Position your cursor over any part of the Color Settings window to read a brief description of a profile or option.

CREATING CUSTOM PROFILES

Photoshop gives you the option to create custom profiles for all working spaces. For instance, CMYK custom workflows can use Photoshop's default presets, a custom ICC profile (preferred), or custom settings for a particular printing press. To establish custom CMYK settings, from the Working Spaces CMYK pull-down menu, select the top option, Custom CMYK, which will bring up the Custom CMYK window.

In the Custom CMYK window, you can select the Ink Options and, more importantly, the Separation Options. When a file is converted to CMYK, the values and percentages of ink that will be resident on each of the C, M, Y, and K channels is critical information for the printing press because those numbers represent how much ink will be applied to the paper during a press run. For instance, a web press applies much less ink than a sheet-fed press does. The first consideration is the separation method, and the two choices are GCR (Gray Component Replacement) and UCR (Under Color Removal). Once you select one of these options, you can then establish the other properties, such as Black Ink Limit, Total Ink Limit, and, in the case of GCR, UCA Amount (percent of Under Color Adjustment), if any.

When you're working without a custom ICC profile, this setting is certainly the key to establishing the proper method for converting to CMYK in Photoshop. Obtaining this type of information today is quite easy. Just ask your prepress house or even the printing company for the information. (Early on in digital prepress history, this information was not so easy to get.) Once the profile is set up this way, it can ensure a great press run.

In this example, using the data from my printer, I created a GCR separation setup using 90% Black Ink Limit and 320% Total Ink Limit with 0% UCA. Also notice that I've named this with my tag, TMAX.


With More options selected, you can also create a Custom RGB profile, but we used Custom CMYK in this example because it's used by more photographers


4.1.3. Saving Your Color Settings

Whether you choose customized or established settings, be sure to save them by clicking the Save button. A dialog box will appear in which you can name your settings something useful; I've named mine TMAX3. When you save your color settings, a Color Settings Comment window will appear, so you can type in any specific instructions or comments regarding your color settings.

Saving these settings will create a .csf file in the Applications Support folder in your system. You can send this file other workstations. From the Color Settings window, select Load to load the same settings on the new workstation without having to match the settings manually.

If you are using Adobe's entire Creative Suite, you may notice the Synchrionized or Unsynchrionized icon in the upper-left corner of the Color Settings dialog box. You can synchronize your color settings across all the Creative Suite applications by choosing Edit Creative Suite Color Settings in Bridge. Here, you can choose any of your saved color settings, which will then be applied to all of the Suite applications. Once youre back in the Color Settings window, the settings will then show the Synchronized icon.


4.1.4. Assigning Versus Converting Profiles

In the course of a normal workflow, assigning profiles isn't a usual procedure. However, as this illustration shows, assigning a different color space to an image can contract or expand the appearance of the color gamut and gamma, depending on the original color space (Adobe RGB (1998) in this example).

It's important to understand the distinction between assigning and converting profiles. Converting profiles will maintain the same color appearance while actually changing the numeric pixel data. Assigning profiles will not change the numeric pixel data but can indeed change the color appearance.

Assigning profiles is most successful when assigning an input profile from the device in which the image was originally created, such as assigning a scanner profile after the scan, and then converting it to a working space. (This is, however, done mostly within the scanner software so it remains seamless.)

To assign a profile from the main menu in Photoshop, select Edit Assign Profile. In the Assign Profile dialog, "Dont Color Manage This Document" allows you to untag a color space via the selection. Using the second choice, you can apply your working color space. The third choice gives you a drop-down menu that shows the profiles available in your system. With Preview checked, you can easily see how assigning a different profile will affect the appearance, but the numeric pixel data will remain the same. Think of this as placing a filter of sorts over the image.

If you set your Color Settings set to "Ask When Opening for a Missing Profile" and you open a document with no profile embedded, you will be given options to assign your working space or assign a profile. You can then choose from the same pull-down menu as discussed in the previous section.


Converting profiles does indeed change the pixel data. However, because Photoshop automatically takes advantage of the CMS (as explained in Chapter 2), when you choose "Convert to Profile" in Photoshop, you will see very little (if any) changes in the color appearance because Photoshop is considering the color space of the file and the color space it is converting to before displaying this information through your monitor's calibrated profile. In this way, Photoshop automatically emulates what is known as a "proof view."

And speaking of proof view, you can proof your colors by choosing View Proof Setup Custom and then selecting the ICC profile that you will be printing to. Photoshop will display your image as if it had been converted to that profile. Using Proof Setup will emulate out-of-gamut colors and tones, allowing you to make corrections and adjustments in the files current space if needed. Designed primarily to help view out-of-gamut color when converting from RGB to CMYK, this feature works with any output ICC profile.




Practical Color Management. Eddie Tapp on Digital Photography
Practical Color Management: Eddie Tapp on Digital Photography
ISBN: 0596527683
EAN: 2147483647
Year: 2006
Pages: 61

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