TABLE OF CONTENTS Color plays an important role in the content of many forensic images, including red blood on clothing, the purple of a ninhydrin fingerprint, contrasting colors of a license plate, and ink tints on a questioned document.
Color isolation techniques can be used to take advantage of the color values and reduce the effect of background colors, increase the tonal contrast of different colors, or isolate the colors to extract information from an image.
When color information is in an image and may be beneficial in extracting image detail, one of the first things I do in my image analysis is to view the image in a variety of color spaces and then isolate each color channel. This often will be all I need to clarify an image; otherwise, it works as an excellent first step. That is, this process can show which color space is best for processing the image or which colors are significant in the image to use when using the Channel Mixer as described below.
Images from digital cameras and scanned negatives, slides, and prints are generally in the RGB color space. This means that the color information of the image is from a combination of red, green, and blue values. In Photoshop, images can be viewed in other color spaces, including CMYK (cyan, magenta, yellow, black) and Lab color (one lightness channel and two color channels). By viewing images in different color spaces, you can separate their channels and frequently isolate specific colors...
