Creating profiles of your input devices

A profile of an input device (sometimes called a source profile) describes what colors a device is capable of capturing or scanning. For example, the profile might tell the color management system that a specific camera tends to render the colors in a particular scene with a slightly warm cast. This information is not so the color management system will correct the warm cast, but so the color management system will faithfully represent the warm cast when sending color values to the computer monitor.
Digital camera profiles
Generally describe the camera's behavior when used with a specific lighting source in a specific environment. For example, different profiles are needed for the different light sources you use. Different profiles are also needed for the different qualities of daylight, such as sunny, overcast, shade, early morning, and sunset.
Scanner profiles
Describe how a scanner captures the colors in a print or transparency. For critical color work, some photographers create separate profiles for each type or brand of film scanned on a scanner.
Creating an input profile involves photographing or scanning a color target. For the camera profile, the target must be photographed under the lighting conditions that the profile needs to describe. Third-party software and hardware read the RGB colors in the captured or scanned image. These values are compared with the actual color values that should be in the targets (referencing a device-independent color space like Lab), and the input profile is created.
There are different opinions on whether an input device profile is absolutely essential for producing consistent color. Some users feel that consistent color is difficult to achieve without a source profile. Others feel that regardless of an input device's behavior, a well-calibrated and profiled monitor will accurately display an image's colors for successful color correction.