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Perspective, in context of vision, is the way in which objects appear to the eye based on their spatial attributes, or their dimensions and the position of the eye relative to the objects. In photography, the lenses depict depth and volume and show the physical relationship between various foreground and background elements within the shot. This characteristic is called "perspective," and it plays an important role in the audience's perception of the visual information contained in the video space

Normal perspective shows us the natural depth and juxtaposition of elements as though our eyes were viewing the scene from the camera's position

Using Lenses to Vary Perspective

(a) This figure was shot with a medium focal length lens to produce a "normal" perspective as our eyes would see it.

(b) A wide-angle lens exagge¬rates the distance between the foreground and back¬ground subjects.

(c) The telephoto lens compresses distance making the subjects appear almost next to each other

In this series of shots, the subjects remained stationary. Figure (a) was shot with a medium focal length lens to produce a "normal" perspective as our eyes would see it. In figure (b) a wide-angle lens exaggerates the distance between the foreground and background subjects. In figure© the telephoto lens compresses distance making the subjects appear almost next to each other. Depth of field is also changed, becoming shallower with the telephoto lens.

The particular focal length you choose for any shot depends on a number of considerations as well as the visual perspective you wish to provide for the viewer. We will discuss the use of lenses in production by dividing them into three broad focal length groups: normal angle lenses, wide angle lenses, and narrow angle lenses.

Normal or Standard Lenses

FIELD OF VIEW A normal lens provides approximately the same field of view as our eyes do In 16-mm format, a "normal" lens is approximately 25 to 35 mm. PERSPECTIVE A normal or medium angle lens produces natural depth perspective with no exaggeration of foreground-to-background subject size, depth, or speed of movement. DEPTH OF FIELD Normal lenses generally provide a medium depth of field with objects at the extreme foreground and background areas of the picture thrown slightly out of focus, but with a fairly wide area of acceptable focus around the principal subject

MOVEMENT The movement of subjects toward or away from the camera appears at normal speed. Similarly, camera movement is not exaggerated but appears natural to the viewer. It is rather easy to follow a moving subject on a medium or normal angle lens since the magnification is not very great. Camera movement can be accomplished smoothly on a normal lens although extremely mobile camera moves should not be attempted on this lens since the jitter and shake of a moving camera can appear obvious.
DISTORTION Normal angle lenses produce almost no apparent picture distortion. The very slight flattening effect they produce can be quite flattering for many subjects as it tends to deemphasize some prominent facial features

Wide Angle Lenses

FIELD OF VIEW The wide angle lens provides a very wide horizontal field of view with very little Image magnification. Principal subjects appear relatively small in relation to the, overall background, and it is somewhat difficult to discern much detail in a very wide shot. In 16 mm format size, most wide angle lenses have focal lengths from about 12 to 25 mm. However, there are some extremely wide angle lenses with focal lengths as low as 6 mm, which are used for special purpose applications.

PERSPECTIVE Wide-angle lenses force perspective and exaggerate the impression of depth and distance. The forced perspective makes foreground subjects appear much larger than background elements.

DEPTH OF FIELD Wide-angle lenses produce a very deep depth of field in which virtually all elements within the frame are in focus.

MOVEMENT The wide-angle lens exaggerates the speed of subject or camera movement. Objects tend to grow' in size and to recede very rapidly. Subject movement is very easy to follow on the wide-angle lens, since the wide horizontal view, minimal magnification, and deep depth of field eliminate camera jitter and focus problems. The wide-angle lens is an excellent choice when you must move your camera on the air, particularly for complex movements or for hand-held cameras, since the low magnification and deep depth of field will cover up slight camera shakes and imprecise focusing.

DISTORTION The forced perspective of the lens can result in a distorted image if the subject works too close to the lens. Wide-angle lenses also tend toward "barrel distortion," in which vertical lines appear to bulge outward in the middle of the picture and to converge at the top and bottom.

IMITATIONS The very wide vista on some wide, establishing shots makes picture definition and detail less sharp and may make it difficult for the viewer to see all objects clearly. Also, as the deep depth of field permits little selective focus, foreground, middle,and background objects may compete for the viewer's attention. Finally, the wide-angle lens is highly susceptible to lens "flare" as its wide vista may inadvertently include some-studio lights which can produce a distracting, multicolored effect. Flares are usually eliminated by changing the camera's position, by repositioning the lighting instrument, or by attaching a lens hood in front of the lens to block the light.

Narrow-Angle (Telephoto) Lenses

FIELD OF VIEW A narrow angle lens produces a very narrow field of view with a powerful subject magnification. In 16-mm format, long lenses are generally those with focal lengths running from 100 to about 500 mm. Lenses with focal lengths greater than 500 mm are rarely used, except for special remote applications since their minimum focusing distances are too great for use in the studio. PERSPECTIVE The long lens compresses perspective, reduces the perception of space and volume, and makes all subjects on different depth planes within the videospace appear about equal in size.

DEPTH OF FIELD Long lenses produce a very shallow depth of field with a small area of acceptable focus around the principal subject. The depth of field can be so narrow, in fact, that at close operation distance objects only a few inches from the principal subject may appear out of focus.

MOVEMENT The extreme magnification and narrow horizontal field of view makes the long lens difficult to use for most movement situations. Following a rapidly moving subject is very hard since the focus is so critical and the field of view is extremely narrow. The magnification power of the lens also makes on-air camera movement virtually impossible since the magnification of the lens will emphasize the slightest camera shake or jitter. For this reason, long lenses should never be used on a portable camera unless the camera is used on a tripod or on a strong, sturdy camera brace.

DISTORTION The compression of perspective tends to flatten a subject's features and the depth perspective in the shot. The lens may magnify heat waves from the ground when used for extremely long distances on remotes, which can make the image appear wavy and distorted.

LIMITATIONS On-air camera movement is virtually impossible, and following moving subjects must be carefully planned in advance

Effects of Perspective

Perspective can be used to enhance the visual meaning of shots. Most television studios took larger than they really are owing to the director's use of a wide-angle lens to force perspective and exagge¬rate depth and volume. Auto manufacturers fre¬quently shoot their car commercials and adver¬tisements with a short focal length lens to make the car look longer and more streamlined than it really is. In general, wide-angle lenses which force perspective tend to make space appear larger than in reality and make subjects appear much more powerful and dominant. The opposite effect is provided by the com¬pressed perspective of the telephoto lens. In this case, the lens flattens out subjects, compressing depth and equalizing the size of foreground and background objects in the picture. This perspec¬tive can be quite effective when used with script material which calls for such a visual impression. For example, on a documentary about over¬crowding in a college town, the director used a long, telephoto lens to shoot down a row of parked cars. The lens squeezed the cars together and apparently eliminated the space between them, conveying to the viewer the idea of a crowded, congested area which perfectly complemented the programmer's script? An example of the use of the telephoto lens to slow down subject movement can be seen in the film 'The Graduate'. At one point, the main character is shown frantically running toward the camera, but the long lens' makes it appear on screen as though the hero is running on a treadmill, huffing and puffing, but seemingly getting no closer for all his effort.

Lens Focal Length	Terminology	Typical Photography
Less than 21 mm	Extreme Wide Angle	Architecture
21-35 mm	Wide Angle	Landscape
35-70 mm	Normal	Street and Documentary
20-135mm	Medium Telephoto	Portraiture
135-300	Telephoto	Sports, Birds, Wildlife

DISTORTION FIGURE Telephoto Depth Compression. The use of a long focal length lens makes the dumbbells appear as though they are so close they are touching each other and unintentionally distort the viewer's spatial perspective. Of course, there are some production situations in which we might wish to avoid the particular effects of forced or compressed perspective.

A wide lens's forced perspective can also occasionally produce unintended distortion, par¬ticularly when a subject works too close to the lens and his facial features are distorted into the familiar "banana nose" or "elastic arm" effect (See Figures) FIGURES- Wide Angle Lens Distortion.The forced perspective of a wide-angle (short focal length) lens can result in a distorted image. In above figure (the subject's feet appear unnaturally large in relation to her body.

In this figure (the dog's body appears elongated, and her head and shoulders appear unnaturally larger than normal proportions Other Lenses Other Lenses: are used in clicking close-up shots giving the original size of the object in the ratio of 1:1. For e.g.: An object which is 10mm will come into view as 10mm on the 35mm frame. This lens shows the original size of the image in any picture frame. Angle of view is narrower than 25

Fish eye lenses: These lenses are used to distort the perceptive lenses, creating a fish eye image in 180°. Focal length varies from 7~16mm. These are specialized lenses in picking the correct images and can produce memorable images.

Super wide angle lens: Focal length is < 24mm. This lens show great exaggerated perspective in images and restricts vantage points. This lens is widely used by real estate agents in promoting their estates.

Super telephoto lens: Focal length is > 300mm. These longer telephoto lenses are of high price and offer the same quality. You need a tripod to carry the camera, which is attached with a super telephoto lens. This lens is very heavy, often the weight of the lens yield images with a shake. It is used by tabloid journalists when spying on celebs.

GLOSSARY:

Focal Length: The focal length of a lens determines its angle of view, and thus also how much the subject will be magnified for a given photographic position. Wide angle lenses have small focal lengths, while telephoto lenses have larger corresponding focal lengths