Section 5.3. CM and Scanning: In Depth

5.2. Profile Editing

Profile editing is no more than changing an ICC profile if it doesn't work exactly the way you want it to. If you know how to use the various tools to correct images in Photoshop, then you should be able to edit profiles.

With a properly calibrated and profiled device, you should be able to achieve relatively accurate color. For most photographers, this workflow will work very well, and no further work will be needed. However, if you are more demanding or if you find limitations to the profile, then you may want to consider editing the profile.

Some profiling software allows you to use different settings and options to achieve better color when creating the profile. Standalone editing software applications or modules, which allow you edit a profile after it has been created, are also available.

Before editing a profile, however, you will need to print out a variety of different images to get an overall idea of how the profile is responding. Profile editing is not used to fix a specific image problem, but is instead used to fine-tune the profile for a variety of work. In other words, this kind of adjustment is used for fixing a whole category of images rather than a single one.

5.2.1. Profile-Editing Applications

Your first option is to change some of the settings in your profiling application itself. For instance, MonacoPROFILER gives you numerous options when you're actually creating the profile. (Note that the settings that control color are available only for the perceptual rendering intent.) These controls are fairly limited and are global controls as opposed to selective controls.

The main way of editing a profile is with a standalone profile editor, such as GretagMabeth's ProfileEditor. There are other profile-editing software applications on the market. Each has its own unique way of editing, but if you understand editing color within Photoshop, you should not have any difficulty with any of them. This software will edit input, monitor, and output profiles, even those created by other ICC-profiling applications. Let's take a look at editing a profile in ProfileEditor.

You can edit a profile by itself or in combination with other profiles. Even if you are editing just one profile, it is generally recommended that you select both the source and destination profiles, as shown in the figure, and then edit the one you want.

For this example, we'll edit Pro4000 Photo Qlty IJP, an RGB profile. For this example, we used AdobeRGB1998.icc as the source profile because many photographers use it as their standard RGB working space. Before editing the printer profile, you need to pick the rendering intent that you wish to edit, which in this example is Perceptual. You also need to have your monitor calibrated and profiled because the editor uses this as the System Profile. This System Profile allows you to preview a standard test image that you are going to edit. Select the file using Open Image. This image should be in the same color space as your source profile. It's important that your standard test image is accurate; you should probably use a commercially available test image, such as the DIMA test image.

Once you have selected the printer profile, there are many tools that you can use to edit it. The tools are laid out from top to bottom in the order that they should be used, although you don't have to use them all. The first tool that we'll use in this example is the Gradations tool, which you can use to fix the overall tonality (lighter, darker, contrast, etc.) by moving all the curves at once. You may also edit each curve individually to fix an overall color-balance problem or color problems anywhere on the tonal scale.

If you know how to edit curves in Photoshop, you should have no difficulty using the Gradations tool within ProfileEditor. When you make changes to the curve, the sample image will change also. On the top and left side of the image window, there are two sliders that can be moved so that you can see the effect of the profile both before and after the edit. Also, as you edit the image, you can view the numerical readouts (Values) of a specific point within the image by selecting the eyedropper at the top of the image window and clicking the area of the image for which you wish to see the numbers. A small color box visually shows the before and after. (The Values are affected by all of the tools.)

Another very useful tool is Global Correction, which allows you to adjust the overall Lightness, Contrast, and Saturation of the image.

The Selective Color tool is very powerful. Selective Color allows you to adjust a very specific color or small range of colors without affecting other colors. Let's say you have a certain red that, even with a profile, appears to be too orange and light. To fix this problem, you need to remove some of the yellow from the red and darken it. The first step is to open the Selective Color tool. This tool allows you to make multiple selective color edits, but for this example, you are going to make just one red edit. Click on the Add button to create the first edit. Next, click on the leftmost eyedropper and select the red color in the image that you wish to edit. The first selection will be a very narrow range of color, but you have the ability to add to the selection by either moving the sliders or using the plus eyedropper. If you pick too much color, you can use the minus eyedropper.

You can edit an image in the color spaces LCH and LAB. LCH is probably a more intuitive color space with which to work; L is the lightness, C is chroma (saturation), and h is hue (color).

By selecting the Range Preview box, you can show the range of colors that you wish to edit in green. If you turn off the Range Preview, then you will see the image without showing the range, even though you have selected it.

Once you have picked the color (Selected Color) that you want to edit on the left side, you will then transfer this color to the Edited Color side by clicking on the double-right arrows (>>). From this point on, you will adjust the new color by either using the LCh sliders or changing the numerical values. In our example, to darken the red slightly and take a little yellow out, the L was lowered a bit and the h was moved a little from the yellow. The sample image in the window reflects this change.

Once you have made all the edits to the profile, you will need to save it. When saving the profile, you can save only for the device and rendering intent that you initially selected, for different rendering intents, or for soft proofing. Naming conventions are important, so my recommendation here is to use the original name of the profile and add E1 to to indicate Edit 1.

Because you may have to do several edits to a profile after printing to see how the edit actually performs, you can then name the next profile E2, and so on. Note that it is best to print a variety of test images with the edited profile because one image may not be representative.

In this example, we used output device and single rendering intent only. While this doesn't cover all of the different options, it should give you a preliminary introduction to profile editing.

Input profiles from scanners and digital cameras may also be edited with ProfileEditor or other profile-editing software.