Lens focal length and field of view are two key specifications that determine the angle of view and level of magnification. Focal length is measured in millimeters and indicates how much the lens magnifies or crops the scene. A wider-angle lens with a lower focal length will capture a broader field of view, while a telephoto lens with a higher focal length provides tighter magnification. For example, a standard zoom on a DSLR may range from 18-55mm, covering wide angle to short telephoto.

Aperture, Shutter Speed, and Depth of Field

In addition to focal length, the aperture, or f-stop setting, of a Camera Lens  impacts key photographic factors such as depth of field and exposure. Apertures are numbered in f-stops that correspond to precise diameter openings in the diaphragm located inside the lens. Lower f-stop numbers like f/1.8 and f/2.8 refer to wider apertures that allow more light to reach the sensor or film plane.

Wider apertures result in a shallower depth of field, wherein a narrower zone is sharply focused both in front of and behind the point of focus. This creative effect is useful for isolating subjects against a softly focused background. Conversely, using a higher f-stop like f/8 or f/11 creates a deeper depth of field with a greater portion of the scene in focus from near to far.

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