1. Introduction

iCorrect EditLab is a color correction and color editing filter plug-in for Adobe Photoshop and other Adobe imaging programs. The iCorrect EditLab plug-in makes global color corrections based on:

• an automatic analysis of your image,
• analysis of certain reference or "memory" colors that you identify in your image,
• interactive dialog control settings, and
• Photoshop's color management setup.

EditLab works in "SmartColor" mode (a mode that intelligently sets the editing controls based on the color content of the image), in manual mode, or in a combination of the two.

Many of the tools and much of the philosophy behind EditLab are the result of the observation that almost everyone knows what certain colors should look like. When an image is viewed, it is surprising how easily color errors are seen, even by people untrained in this discipline. For example, everyone knows that snow is white (neutral) and what skin, foliage, and sky blue should look like. If an image shows a person's face that is bright red, the observer knows that the color is wrong, even though he may never have seen the actual person in the image. These common reference or "memory" colors form the basis of EditLab's approach to improving the color of an image. EditLab's tools include:

• color balance,
• black and white point selection,
• brightness/contrast/saturation controls, and
• hue selective editing.

In many production environments, color management, using ICC device profiles, is rapidly becoming the preferred method of producing color-accurate digital images. While this may be the best way to control color reproduction in many situations, it isn't always possible. There are large classes of digital images of unknown pedigree. It is not possible to use device profiles to relate the colors in these images to any device-independent reference because the profiles do not exist and cannot be made after the fact. For example, you may not have any information about how images on a stock photography CD-ROM were acquired. EditLab can be used to quickly and easily correct uncalibrated images such as these, transforming them into a calibrated color space.

Four Ways to Use EditLab

iCorrect EditLab has a very powerful tool set for creating a color correction function. Although this is a great way to fix a particular color problem, this power can be leveraged even further in the way in which the color correction function is used. EditLab can operate in any of four modes:

• The color edit may be applied to the image itself, providing a nice way to color correct several images, each having a different color problem.
• The color edit may be applied to an existing ICC input profile. In this mode, EditLab is an ICC input profile editor.
• The color edit may be saved as an ICC input profile which may be assigned to any number of other images. In this mode, you can create ICC profiles by eye, without the use of color charts or instruments.
• The color edit may be saved as a ColorCircuit file, which may later be applied to large numbers of other images using the ColorCircuitQ application program.

Chapters 4 through 7 describe EditLab's color editing tools, which will be used regardless of the mode in which EditLab is run. Once these editing skills have been developed, you will then learn in chapter 8 how they may be applied to each of the four modes.

Very Important Photoshop Setup Information!

iCorrect EditLab will always correct the color of an image to Photoshop's currently selected RGB working space. Therefore, it is critical that you have Photoshop set up in a way that allows iCorrect EditLab to perform properly. Here is a checklist:

1. Calibrate your monitor and load its profile as the system profile.
   The manner in which you do this depends on both the platform you are on and the operating system version you are running. Your monitor profile affects the way in which colors are displayed in Photoshop, and also in iCorrect EditLab. If your monitor profile is bad, colors will not look right.
   
   
2. Select a "normal" RGB working space in Photoshop.
   Normal working spaces are theoretical in nature and have certain "nice" properties, for example, a neutral color by definition has its red, green and blues values equal to each other.
   
   
3. Never select your monitor profile as your RGB working space.
   Monitor profiles generally do not have the "nice" properties discussed above that theoretical working spaces should have. Incidentally, Adobe also recommends against using your monitor profile as a working space.
   
   
4. If your image has an embedded profile, convert it to the working space before using iCorrect EditLab.
   This may be done when the image is first opened, or it may be done with Photoshop's "Image > Mode > Convert to Profile…" command.
   
   
5. If your image has no embedded profile, assign the working space profile before using iCorrect EditLab.
   This may be done when the image is first opened, or it may be done with Photoshop's "Image > Mode > Assign Profile…" command.

Photoshop's working space is selected with its "Color Settings" dialog for versions 6 and 7, or with the "Color Settings / RGB Setup" dialog box with version 5 (also check the "Display Using Monitor Compensation" checkbox). If you are running an even earlier version of Photoshop, be sure that the settings in the Monitor Setup dialog box accurately describe your monitor.

Once you are properly set up, iCorrect EditLab will correct your image to Photoshop's working color space (Photoshop 5.0 and later) or to the color space defined by the Monitor Setup parameters (Photoshop version 4 and earlier).

Here is a suggested Color Settings set up that will help make sure your image properly ends up in the working space (shown for Photoshop 7.0):

If you are using the plug-in with an application other than Photoshop, you should be aware that not all applications provide the same color management setup information that Photoshop provides. If iCorrect EditLab cannot get this information about color settings from your application, it will correct the image into