Depth of focus is a lens optics concept that measures the tolerance of placement of the image plane (the film plane in a camera) in relation to the lens. In a camera, depth of focus indicates the tolerance of the film's displacement within the camera, and is therefore sometimes referred to as "lens-to-film tolerance."

While the phrase depth of focus was historically used, and is sometimes still used, to mean depth of field, in modern times it is more often reserved for the image-side depth.

Depth of field is the range of distances in object space for which object points are imaged with acceptable sharpness with a fixed position of the image plane (the plane of the film or electronic sensor). Depth of focus can have two slightly different meanings. The first is the distance over which the image plane can be displaced while a single object plane remains in acceptably sharp focus; the second is the image-side conjugate of depth of field. With the first meaning, the depth of focus is symmetrical about the image plane; with the second, the depth of focus is greater on the far side of the image plane, though in most cases the distances are approximately equal.

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The field of view (also field of vision, abbreviated FOV) is the extent of the observable world that is seen at any given moment.

Different animals have different fields of view, depending on the placement of the eyes. Humans have an almost 180-degree forward-facing horizontal field of view, while some birds have a complete or nearly complete 360-degree field of view. In addition, the vertical range of the field of view in humans is typically around 100 degrees.

The range of visual abilities is not uniform across a field of view, and varies from animal to animal. For example, binocular vision, which is important for depth perception, only covers 120 degrees (horizontally) of the field of vision in humans^{[citation needed]}; the remaining peripheral 60 degrees have no binocular vision (because of the lack of overlap in the images from either eye for those parts of the field of view). Some birds have a scant 10 or 20 degrees of binocular vision.

Similarly, color vision and the ability to perceive shape and motion vary across the field of view; in humans the former is concentrated in the center of the visual field, while the latter tends to be much stronger in the periphery. This is due to the much higher concentration of color-sensitive cone cells in the fovea, the central region of the retina, in comparison to the higher concentration of motion-sensitive rod cells in the periphery. Since cone cells require considerably brighter light sources to be activated, the result of this distribution is that peripheral vision is much stronger at night relative to binocular vision.

Richard Stewart is the current mayor for the city of Coquitlam, British Columbia. Stewart was elected to Coquitlam City Council in 2005. He is bilingual (English and French). Stewart has lived all his life in Coquitlam. He was married in 1983 to Anna Rosa, they have four children. Stewart has served his community in the provincial government as MLA for Coquitlam-Maillardville 2001-2005; appointed MLA Responsible for Francophone Affairs, member of the Government Caucus Committee on the Economy, and Chair of the Select Standing Committee on Education.

At the local government level, Stewart has served on Economic Development Committees, on a local Advisory Design Panel, on Housing Committees, and as a Trustee on the Coquitlam Public Library Board. Stewart is a writer, and has operated his own publishing, government relations and communications business.

On November 15, 2008, Stewart was elected as mayor of Coquitlam in the British Columbia municipal elections, beating out incumbent Maxine Wilson.