Glossary of Digital Photography Terms – Part 4

Single-lens reflex (SLR) – is a type of camera that uses a movable mirror placed between the lens to show the image that will be captured in a viewfinder.
Digital single-lens reflex camera (digital SLR or DSLR) – is a digital camera that operates on the same optical and mechanical principles as a film single-lens reflex camera.
Exposure compensation – is a technique to compensate a measured exposure level against other factors which may render a less-optimal image (filters, non-standard processing, or intended under or overexposure).
Focal length – is a measure of how strongly it focuses or diverges light.
Telephoto lens – is a specific construction of a long focal length photographic lens that places its optical centre outside of its physical construction, such that the entire lens assembly is between the optical centre and the focal plane.
Wide-angle lens – is a lens whose focal length is substantially shorter than the focal length of a normal lens for the image size produced by the camera.
Normal lens – is a lens that generates images that are generally held to have a “natural” perspective compared with lenses with longer or shorter focal lengths.
F-number – is the quantitative measure of lens speed, in other words, the diameter of the entrance pupil in terms of the effective focal length of the lens.
Angle of view (Field of view) – describes the vertical and horizontal extent of a given scene that is imaged by a camera.
Viewfinder – is what the photographer looks through to compose, and in many cases to focus, the picture.