Vistek Imaging and Photographic Terminology Database

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h

H&D curve: Another name for the D/log E curve, after its originators, Ferdinand Hurter and Vero C. Driffield.

Halation: Is a diffused ring of light typically formed around small brilliant highlight areas in the subject. It is caused by light passing straight through the emulsion and being reflected back by the film base on the light sensitive layer. This records slightly out of register with the original image.

Halftone image: An image reproduced through a special screen made up of dots of various sizes to simulate shade of gray in a photograph. Typically used for newspaper or magazine reproduction of images.

Halftone screen: A pattern of dots of different sizes used to simulate a continuous tone photograph, either in colour or black and white.

Halo: A light line around object edges in a image, produced by the USM (sharpening) technique.

Hard drive: A built-in or off-line fixed storage medium which holds large amounts of data that can be accessed rapidly depending on the power of the computer.

Hard proof: A printed proof of an image or document, intended to accurately convey colour. Contrast with soft proof.

Hardeners: Are chemicals often used with a fixing bath to strengthen the physical characteristics of an emulsion. The most common hardeners are potassium or chrome alum.

Header: Technical information packaged with an image file, which may be of use in displaying the image (e.g., length and width in pixels), identifying the image (e.g., name or source), or identifying the owner.

High-bit: An RGB system or image containing more than 24 bits of colour data per pixel.

Highlights: The whitest or brightest part of an image; the opposite of shadows.

Histogram: A graphic representation of how brightness and darkness pixels are distributed in an image. A histogram skewed heavily to the left indicates a dark image, while a histogram skewed to the right indicates a light image.

History palette: The history palette lists the actions that have been done to an image and allows you to step forward or backward to a certain point.

Honeycomb: Grid which makes light from a flash (or other source) more directional, like a spot rather than a flood.

Horizontal Resolution: The number of vertical lines that a system is capable of producing (counted on a horizontal axis).

Hot Shoe: A flash connector generally found on the top of the camera that lets you attach a flash unit and trigger it in sync with the shutter.

HSL: Hue, Saturation, and Lightness. A method of describing any colour as a triplet of real values. The hue represents the colour or wavelength of the colour. It is sometimes called tone and is what most people think of as colour. The hue is taken from the standard colour wheel and is thus calibrated in degrees about the wheel. Saturation is the depth of the colour. It states how gray the colour is. It is real valued parameter from 0.0 to 1.0 with 0.0 indicating full gray and 1.0 representing pure hue. The lightness is how black or white a colour is. It also ranges from 0.0 to 1.0 but with 0.0 representing black and 1.0 white. A lightness of 0.5 is pure hue.

HTML: Hypertext Markup Language. An encoding format for identifying and linking electronic documents used to deliver information on the World Wide Web.

Hue: The aspect of colour that distinguished it from another colour (what makes a colour red, green, or blue). Hue is distinct from saturation, which measures the intensity of the hue.

Hue error: The degree of contamination in a process colour ink or other pigments that alters its appearance from that of a perfect process colour. For example most magenta inks are contaminated with yellow, making them appear to be red, rather than purplish-red.

Hybrid Imaging: Electronic imaging systems that mix traditional silver-halide technologies with digital imaging technologies.

Hyperfocal distance: The distance to the nearest plane of depth of field ( the nearest object in focus) when the lens is focused on infinity. Also the distance to the plane of sharpest focus when infinity is at the farthest plane of the depth of field. Focusing on the hyperfocal distance extends the depth of field from half the hyperfocal distance to infinity.

Hyperlinks: Typically text, but also graphics, that serve as links that let you move around on the Internet and connect to different web sites. Hyperlinks are usually blue and underlined.

Hypo: A common name for any fixer; from the abbreviation for sodium hyposulfite, the previous name for sodium thiosulfate (the active ingredient in most fixers).

Hz: An abbreviation for hertz-an international unit of frequency which equals one cycle per second.