5.7. EVALUATING COLOR AND CONTRAST
Understanding and judging color and contrast in your images are essential to producing good photography. Your lenses are where color and contrast begin and, to some extent, where they are controlled as they are processed as an exposure before being converted into a digital image.
Histograms are available for you to use as an evaluative tool on your camera's LCD, as well as later in software image-editing applications. These graphs, which give you information about shadows, highlights, midtones, and colors in your images, provide a quick view as to your overall exposure quality and insight on how to adjust it, if necessary. There are two types of histograms: luminance and RGB.
5.7.1. LUMINANCE HISTOGRAMS
Every digital image has a tonal range that includes all the colors from the brightest to the darkest in red, green, and blue (RGB). Histograms more commonly come in a black-and-white mode where red, green, and blue are averaged; these are called luminance histograms. Your camera shows luminance histograms on the LCD, and your image-editing software often defaults to this mode.
The luminosity of an image refers to the overall distribution of brightness in a digital photo, and it takes into account your eye's sensitivity to different colors (for example, red and blue appear less bright than green to the human eye). Luminance histograms calculate a weighted average of RGB colors in an image to create a single representation of the image that is ...