Lens Focal Length

Lens is described by its focal length, which is the distance in millimeters (mm) between the lens and the image it forms on the sensor or film, when it is sharply focused at infinity (the farthest possible visual distance). Focal length determines the angle of view or how much a lens sees which controls what portion of a scene will be captured. Focal length of a lens controls how wide or narrow its perspective is. A lens with a wide perspective will provide an expansive view while one with an intermediate perspective will offers you a normal view of a subject. A narrow, telephoto view might bring details of a subject in very close.

Focal lengths are measured in millimeters. Some lenses have a field of view that is fixed at a particular focal length, such as 18mm, 50mm, 105mm, or 200mm. These are called prime lenses or, sometimes, fixed focal length lenses. Other lenses have the ability to shift lens elements around to produce a continuous range of focal lengths. These are called zoom lenses. A typical zoom lens might be able to change magnifications from an 18mm wide view to a 200mm telephoto perspective, thus incorporating the fields of view of the 18mm, 50mm, 105mm, and 200mm prime lenses listed previously, plus all the focal lengths between them.

Some lenses have a field of view that is fixed at a particular focal length, such as 18mm, 50mm, 105mm, or 200mm.

The most common focal lengths can be grouped into general categories, with, of course, some overlap between adjacent groups. The following list shows the approximate focal lengths of lenses used, with a little overlap in focal lengths between some categories.

Ultra-Wide Angle Lenses: 10-15mm

These lenses capture the broadest view of a scene than a standard lens does by making subjects appear smaller than they would with a normal lens. It offer tremendous depth of field, thus permitting one to get very close to a subject and produce exaggerated size relationships, unusual perspectives due to distortion, and an intimate viewing experience which can be intentionally used to generate visual interest.

Wide Angle Lenses: 16-28mm

These lenses are used for most landscape, architecture, and interior photography, or any subjects where you have a wide field of view. A wide angle lens is handy for large scenes and in locations where it is not possible for one to move back far enough to photograph the entire scene.

Camera Focal Length

Normal Lenses: 28-40mm

This focal length range is defined separately because, before zoom lenses became predominant, most cameras were purchased with a normal lens. Normal focal lengths are good for 3/4 and full-length portraits, or shots of small groups.

Short Telephoto Lenses: 40-60mm

Lenses in this focal length range have been traditionally called portrait lenses, because they provide a flattering perspective for head and shoulders portrait images. Focal lengths shorter than this range can exaggerate the size of features like noses that are closer to the camera, at the expense of features like ears, which are farther away and appear to be too small. Focal lengths of about 100mm or longer tend to compress facial features together in a flattening effect.

Medium Telephoto Lenses: 60-135mm.

Lenses in this range are popular for close-up and macro photography, because they let you maintain a little distance between your subject and the camera. That distance makes lighting the subject easier and can be less threatening to small living subjects, such as insects. Medium telephoto lenses are also useful for sports at close range, and portraits.

Long Telephoto Lenses: 135-300mm

These focal lengths are useful for pulling in any subject that’s too far from the camera to fill the frame. You’ll find them helpful for shooting concerts, sports events, and skittish wildlife. Telephoto lenses require solid technique to minimize the effects of camera shake and to manage the reduced range of sharpness these lenses offer.

Super Telephoto Lenses: 300mm and above

Really long focal lengths are most useful to wildlife photographers, who must photograph creatures from hundreds of feet away, or smaller critters from dozens of feet away. Outdoor sports photographers who want to put themselves into the middle of the huddle, at the edges of the scrum, or capture an exciting play from the other side of the stadium or field also benefit from really long focal lengths. It’s true that 300mm just barely qualifies for this category because the really long focal lengths range from 400 to 600mm.

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