Zone System and Digital Terminology

Acutance — The term used to describe the degree to which a negative renders a sharp distinction between adjacent print tones. Acutance is related to negative contrast and shouldn't be confused with image sharpness or resolution. Dilute developers and long development times will increase acutance.

Banding — In a digital image, banding appears as distinct tonal steps where there should be a smooth continuous gradation. This is generally considered to be a problem that is caused by the loss of pixel levels when the image is edited in one of Adobe Photoshop's contrast adjustment tools like the Levels or Curves command. Posterization is another word commonly used to describe this effect.

Bit Depth — A pixel's bit depth is a measure of the number of individual tones of gray or color a pixel is allowed to be in an image, measured in bits of digital memory.

Bitmapped — A bitmapped digital image is one composed of numerous individual tile-like picture elements known as pixels. Bitmapped images are said to be rasterized as opposed to vector-based images that are constructed from mathematically defined shapes and lines.

Bracketing — After using a light meter to determine the "correct" f/stop and shutter speed for a given photograph, you would use bracketing to give the film more or less than this base exposure to achieve the desired result. Bracketing is usually done by adjusting the aperture.

Charge Coupled Device (CCD) — One of the two main types of image sensors used in digital cameras.

Clipping — In digital photography, a light or dark tonal value is said to be clipped when a Photoshop contrast adjustment pushes that value beyond the range of tones that can be rendered.

CMOS (Complementary Metal-Oxide Semiconductor) — One of the two main types of image sensors used in digital cameras.

Color Management — The calibration, profiling, and coordination of all elements in a digital imaging workflow for the purpose of insuring that the final print or other output matches the image represented on the computer monitor as closely as possible.

Colorsync — A color management system introduced by Apple Computer Co.

Contraction — The decrease in negative contrast brought about by using a development time that is less than Normal Development. Contraction is symbolized by N-, followed by the number of zones by which you want to decrease the contrast. For example, N - 2 means decrease the development time below Normal Development enough to reduce a Zone IX negative density to a density equivalent to Zone VII. Contraction is also known as "compaction."


1. Subject contrast refers to the relative difference between the amount of light reflected by the "highlights," or bright areas, of the subject and the "shadows," or darker areas. This difference is measured with a reflected-light meter.

2. Negative contrast refers to the relative difference between the "shadow," or thinner, areas of the negative and the "highlight," or more dense, areas.

3. Print contrast (also called tonal separation) is the ability of the film and printing paper to render a visual distinction between close tonal values. Print contrast increases when a negative is printed on higher grades of paper.

Density — Density is technically a scientific term used to indicate the relative opacity of a negative as measured with a densitometer. The term is commonly understood to mean the relative thickness of silver in the negative.

DPI (Dots per inch) — A measurement of the resolution of a digital photo or digital device, including digital cameras and printers. The higher the number, the greater the resolution.

Drivers — Software associated with digital scanners and printers that controls the functioning and coordination of the device with all other elements of the workflow.

Dynamic Range — The term used to define the total range of tonal values in a digital image. Also referred to as contrast.

Expansion — The increase in negative density brought about by developing the negative longer than Normal Development. Expansions are symbolized by N+, followed by the number of zones by which you want to increase the contrast. For example, N + 2 means to increase the negative's development time above Normal Development enough to raise a Zone VI negative density to a Zone VIII density.

Fall — The term used to indicate the position of any subject's meter reading on the Zone Scale after another meter reading has been placed on a different zone. For example, when the contrast of the subject is Normal, the meter reading for the highlight will fall on Zone VII when the meter reading for the shadow is placed on Zone III.

Gamut — The total range of colors that a digital device can reproduce.

Histogram — A graphic representation of the range of tones from dark to light in a digital photograph.

Important Highlight — The area of the subject that you want to appear in the final print as a fully textured and detailed light gray tone. In most cases, this area will be previsualized as Zone VII. Light clothing, concrete, and fully textured white objects are typical Important Highlight Area subjects.

Important Shadow — The area of the scene that you want to appear in the final print as a fully detailed dark value. This need not be an actual shadow. In most cases, the Important Shadow Area is previsualized as Zone III. Dark clothing, brown hair, and green foliage are common Important Shadow Area subjects.

Incident Light — The light that falls on the subject from the light source; measured with an incident-light meter.

Indicating Arrow — The arrow or pointer on a hand-held light meter that is matched with the indicated meter reading to calculate the meter's recommended exposure. The meter number indicated by this arrow is automatically placed on Zone V.

Interpolation — A mathematical method of creating missing image data to increase the file size and/or dimensions of an image.

JPEG — A standard for compressing image data developed by the Joint Photographic Experts Group.

LCD (Liquid Crystal Display) — A low-power monitor often used on the top and/or rear of a digital camera to display settings or the photo itself.

Megabyte (MB) — A measurement of data storage equal to 1024 kilobytes (KB).

Megapixel — Equal to one million pixels.

Neutral Gray Card — A middle gray (18 percent) card designed for calibrating exposure meters and to serve as a visual reference for color reproduction.Also known as a Zone V card.

Noise — Random patterns of either color or brightness that appear in the shadow areas of digital images when higher ISO settings (400 and above).

Normal a. Subject contrast is said to be Normal when the meter readings of the Important Shadow and the Important Highlight fall on Zone III and Zone VII, respectively.

b. Negative contrast is considered Normal when the negative prints well on a Normal grade of paper, usually paper grade 2 or variable-contrast filter 2.

c. Normal Development is the amount of development for a given film and developer that will produce contrast in the negative that is equal to the contrast of the subject. Normal Development is symbolized by N.

Pixel — Pixels or picture elements are the smallest components of digital images. Digital camera and monitor pixels are the physical units that capture and display digital image data, respectively. Image pixels are the individual "tiles" of color or tone that make up the visible image on a monitor.

Placement — The act of relating any single meter reading to a zone on the Zone Scale through controlled exposure. For example, to place a shadow reading on Zone III, you first meter that area with a reflected-light meter, then stop down two stops from the meter's recommended exposure.

Posterization — See Banding.

Previsualization (also visualization) — The act of mentally picturing a photographic subject in terms of the finished print.

Profiles — A small data file that describes the color idiosyncrasies of each element of a color-managed digital workflow including the monitor and printer for the purpose of providing coordination of color rendition from one end of the process to the other.

Raster Image Processor (RIP) — A raster image processor or "rip" is a highly integrated color management, page layout, and ink-handling system that provides the highest quality results from ink jet printers.

Rasterization — See Bitmapped.

Raw Formats The unprocessed black-and-white data from a digital image sensor before it has been converted or Tone Mapped into a color format that can be edited with an application like Adobe's Camera Raw Utility.

Reflected Light — The light that is reflected from the scene to the camera and meter; measured with a reflected-light meter.

Resolution — For analog photography the term is used to describe a film's ability to record fine detail. For film, good resolution is a function of sharp focus, fine grain, good contrast, and minimum exposure and development.

For digital image files, good resolution is achieved through a combination of increasing the number of pixels per inch in your image and assigning an appropriately high bit depth to each pixel.

Tagging — The process of attaching a profile to a digital image to allow it to be rendered accurately on other color-managed systems.

Textural scale — The range of five textured zones from Zone III to Zone VII.

Tonal range — The difference between the whitest white and the blackest black in a photographic print.

Tonal separation — See "Print Contrast "under Contrast.

Tone — The shades of gray, black, and white in a photographic print.

Tone Mapping—The process of converting a digital image from its raw, linear state to a format that more closely resembles a familiar non-linear distribution of tones.

Value — The light and dark areas of a photographic subject, negative, or print.

Vector-Based Images — A graphic image whose visual characteristics are created mathematically by an application line Adobe Illustrator. As opposed to a digital image composed of numerous individual picture elements or pixels.

Visualization — See Previsualization.

Zone — The basic unit of photographic previsualization and contrast measurement.

a. Any one of ten symbolic tones arranged in order from black to white. This ten-step scale is called the Zone Scale. Each zone represents a small range of tones that can be found in both the final print and the original scene.

b. A unit of photographic measurement equivalent to all other photographic controls according to a ratio of 2 to 1.

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