Black and White Defined

We may casually refer to an image as black and white, but there are subtle distinctions between these types of images and how they should be categorized and processed.

First off, the term itself is in a way, incorrect. The origin of the term “black and white” stems from the fact that early photographic processes produced an image composed of silver halide crystals (the black) and the spaces between them (the white). But the objective was always to produce a continuous tone image, which today we refer to as grayscale.

Gray, by definition, is neutral. But one man’s gray is another’s sepia, and in the pursuit of artistic expression, print toning was born, and with it many ways to add color and preserve the silver halide crystals indefinitely. These prints are no longer grayscale by definition, although tradition allows us to continue to describe them as black and white.

A much better term however is monochrome. Mono meaning one, and chrome meaning color. A print of a single color. Now we can differentiate a grayscale image from a monochromatic or toned image. So the grayscale image and the monochrome image become a subset of the “black and white” image. We can safely misuse the term black and white in this way because a true black and white image would be a bitmap, and this is more of a graphic art format that a photographic one.

Since their goal is to be neutral, grayscale photos can be stored in the Grayscale TIFF image format, which makes them a third of the size of an RGB image. But monochromatic photos, which contain subtle color information, must be saved to a color image format. This can be RGB/TIFF which offers moderate compression or RGB/JPEG, which offers greater but somewhat lossy compression. Because of the reduced color gamut in monochromatic images, sRGB is an ideal color profile to use, ensuring compatibility with a wide range of devices.

Modern applications such as Adobe Camera Raw allow you to apply color toning to a grayscale image, saving space and keeping your options open without having to save to the larger color format.