IF (Internal Focusing) System

A system used where the internal elements in the lens are the only parts that move during focusing. This prevents the physical length of the lens from changing, allows for faster focus, reduces aberrations, and facilitates use of filters that require specific alignment such as polarizers, graduated, etc.

Image

A two-dimensional representation of a scene.

Image Editor

A computer program that enables adjustments to a photo to improve its appearance. With image editing software, it is possible to darken or lighten a photo, rotate it, adjust its contrast, colors hue and saturation, crop out extraneous detail, remove red-eye and more. Adobe® Photoshop®, is the professional image-editing standard.

Image Plane

The area at which a lens forms an image, i.e. the film plane if, and when focused correctly.

Image Resolution

The number of pixels in a digital photo is commonly referred to as its image resolution.

Incident Light

Light as measured as it falls on a surface, rather than light reflected from a surface.

Infinity

In relation to camera focus: the horizon.

Infrared

Light not visible with the human eye. Measured at the red end of the spectrum. Can be photographed with special film.

Infrared Compensation

Index An index on a camera lens used to compensate focusing using infrared film. With most lenses, the plane of sharpness for infrared film is slightly farther away than for normal visible-light photography.

Inkjet

A printer that places ink on paper by spraying droplets through tiny nozzles.

Inverse Square Law

A proven statement in physics, repeatable through experimentation. A given physical quantity (as illumination) varies with the distance from the source inversely as the square of the distance. As applicable to flash photography, doubling the flash-to-subject distance reduces the light falling on the subject to one-quarter.

IR Setting

Mark on lenses for focusing infrared film.

ISO

The International Organization for Standardization (ISO), based in Geneva, is a worldwide federation of national standards bodies from over 150 countries, one from each country. ISO is a non-governmental organization established in 1946. The mission of ISO is to promote the development of standardization and related activities in the world with a view to facilitating the international exchange of goods and services, and to developing cooperation in the spheres of intellectual, scientific, technological and economic activity. ISO's work results in international agreements, which are published as International Standards. "ISO" is not an acronym, it is a word, derived from the Greek isos, meaning "equal", which is the etymological root of the prefix "iso-" that occurs in a host of terms, such as "isometric" (of equal measure or dimensions) and "isonomy" (equality of laws, or of people before the law). As applied to photographic film or digital sensors, it refers to its speed or sensitivity in conjunction with a number, like ISO 100, twice as "fast" as ISO 50.