Lenses
October 22nd, 2019The last subtopic I’m going to discuss with respect to composition is lenses.
The choice of lens can have a significant effect on the resultant image and it’s choice should not be ignored.
With respect to lenses, there are three basic types of cameras: fixed-fixed lens, fixed-zoom lens and interchangeable lens.
Fixed-fixed lens cameras have a permanently attached (the first fixed) single focal length (the second fixed) lens. (A fixed focal length lens can also be referred to as a prime lens.) Probably the most common example of this type of camera is the one in most cell phones; neither the lens itself nor the lens’ focal length can be changed.
In a fixed-zoom lens camera, the lens is permanently attached (fixed) but the focal length is adjustable (zoom). Most entry level cameras are of this type.
Lastly, most mid- to high-end cameras allow for interchangeable lenses. In these cameras the lens is a separate unit that attaches to the camera body using a mounting ring that locks the lens to the camera and provides connectivity for mechanical and electrical control of the lens. Typically there is a wide range of lenses that can be purchased and used with the camera body; some of which are fixed focal length and some which are zoom lenses.
Focal Length
Focal length is a term which refers to how strongly a lens converges rays of light. A short focal length converges rays in a shorter distance and a longer focal length converges rays over a longer distance. That definition bleeds over into our vernacular since we refer to a lens with a long focal length as a long lens, it usually has a long physical length as well.
If you’ve ever used a handheld magnifying glass you’ve had direct experience with focal length. To see something clearly through the magnifying glass you probably had to adjust both the distance between the glass and the subject and the glass and your eye. What you were doing is finding the focal length of the magnifying glass.
Focal lengths are expressed in millimeters (mm) and range from very short (16mm) up through very long (600mm). (For reference, one inch is 25.4mm.) Short focal lengths are referred to as wide angle lenses and long focal lengths are called telephoto lenses. In between these two extremes, in the middle of the range are normal lenses.
(Mituraju Sunrise, Canon 5DMII, EF24-105 @ 28mm, 1/60s, f/8, ISO400)