Monochrome describes paintings, drawings, design, or photographs in one color or shades of one color. A monochromatic object or image has colors in shades of limited colors or hues. Images using only shades of grey (with or without black and/or white) are called grayscale or black-and-white. However, scientifically speaking, monochromatic light refers to visible light of a narrow band of wavelengths (see spectral color).
Monochrome photography is photography where the image produced has a single hue, rather than recording the colours of the object that was photographed. It includes all forms of black-and-white photography, which produce images containing tones of grey ranging from black to white. Most modern black-and-white films, called panchromatic films, record the entire visible spectrum. Some films are orthochromatic, recording visible light wavelengths shorter than 590 nanometres.
Black-and-white photography is considered more subtle and interpretive, and less realistic than colour photography. Monochrome images are not direct renditions of their subjects, but are abstractions from reality, representing colours in shades of grey. In computer terms, this is often called greyscale.
Monochrome images may be produced using black-and-white film or paper, or by manipulating colour images using computer software.
In photography and computing, a grayscale or greyscale digital image is an image in which the value of each pixel is a single sample, that is, it carries only intensity information. Images of this sort, also known as black-and-white, are composed exclusively of shades of gray, varying from black at the weakest intensity to white at the strongest.
Grayscale images are distinct from one-bit bi-tonal black-and-white images, which in the context of computer imaging are images with only the two colors, black, and white (also called bilevel or binary images). Grayscale images have many shades of gray in between. Grayscale images are also called monochromatic, denoting the presence of only one (mono) color (chrome).
Grayscale images are often the result of measuring the intensity of light at each pixel in a single band of the electromagnetic spectrum (e.g. infrared, visible light, ultraviolet, etc.), and in such cases they are monochromatic proper when only a given frequency is captured. But also they can be synthesized from a full color image; see the section about converting to grayscale.