What are ‘Lens Angles’?

The camera’s lens shows us a wedge-shaped segment of the scene. In regular TV/video systems, its horizontal coverage is 1.33 times greater than its vertical; in other words, the screen has 4 by 3 proportions.

How much of the scene appears in the picture will depend on the angles the lens covers. If the lens-covers a horizontal angle of 40°, its corresponding vertical angle will be 30°.

The actual angles will vary with the lens’ focal length (see Glossary). A prime lens’ angles are fixed, according to its design; but zoom lenses have variable focal length, and so can adjust their coverage.

Two conventions are used when planning shots. You can identify the lens either by its ‘focal length’, or by its horizontal ‘lens angle’. Because angles are more obvious, and can be directly related to scale plans, we shall use that method here.

Zoom ratio

The horizontal coverage of a zoom lens can be changed from as little as 1.5° at the narrow angle (‘telephoto’) end of its range to as much as 60° at its wide angle limit.

But most zooms cover a more limited range, and a 10:1 zoom ratio (50–5°) has proved very practical for many purposes.

Image size

The lens angle determines how much of the scene is revealed from a particular camera position. A narrow lens angle (e.g. 10°) may pick out a single face from a row of people. Readjust it to a wide angle (e.g. 50°) and it may show them all. However, although we see more, sizes are proportionally reduced.

• Using a 10° lens, subjects are 5 times as large as with the 50° lens, but we see only as much of the scene.

• On a 5° lens, the subject will appear twice as large as on the 10° lens; 10 times that in the 50° shot.

Lens angle and perspective

Theoretically, subjects are only shown in their true proportions (natural perspective) if the camera’s lens angle is similar to that from the viewer’s eye to either side of the TV screen (e.g. 20–27°); but the eye is very tolerant. However, if you use a much narrower or wider lens angle, pictorial perspective will look distorted. Space, distance and depth appear exaggerated (wide angle) or compressed (narrow). With care, though, as you will see., you can turn these effects to your advantage.

Angle of view

The TV. camera lens ‘sees’ 4 by 3 proportions. The vertical angle of view, is therefore 3/4 of its horizontal angle.

Lens Angle

Changes are proportional as the lens angle alters. Using a lens of three times the present angle (i.e. F), the sybject now appears of former size and ×3 of scene width is now visible. The effect is that of increasing the camera distance by three times. Changing to a narrower angle has the opposite effect.