What are the three types of lenses and what are the characteristics of imaging?

Lenses are divided into wide-angle, medium-focus and telephoto lenses.

1, wide-angle lens

Take a 35mm single lens reflex camera as an example. A wide-angle lens usually refers to a lens with a focal length of 17 to 35mm.

The basic characteristics of a wide-angle lens are its large viewing angle and wide field of vision. The range of scenery observed from a certain viewpoint is much larger than that seen by human eyes at the same viewpoint; The depth of field is long, which can show a fairly clear range; It can emphasize the perspective effect of the picture, be good at exaggerating the foreground and express the sense of distance of the scene, which is conducive to enhancing the appeal of the picture.

2, telephoto lens

The telephoto lens has a viewing angle of less than 20 degrees and a focal length of several tens or hundreds of millimeters. Long focal length lenses are divided into ordinary telephoto lenses and ultra-telephoto lenses. The focal length of ordinary telephoto lens is close to that of standard lens, while the focal length of ultra telephoto lens is much larger than that of standard lens. Take 135 camera as an example, the photographic lens with a focal length of 85mm-300mm is a normal telephoto lens, and the lens with a focal length of more than 300mm is a super telephoto lens.

A telephoto lens has a long focal length, a small viewing angle and a large image on the negative. Therefore, at the same distance, you can take larger images than the standard lens. Suitable for shooting distant objects.

Because its depth of field is smaller than the standard lens, it can blur the background more effectively and highlight the focused subject, and the subject is generally far away from the camera, which makes the portrait more realistic in perspective, so people often call the telephoto lens a portrait lens.

The telephoto lens is often used in professional photography because of its long lens barrel, heavy weight, relatively expensive price and small depth of field, and it is difficult to focus in practical use.

3. Medium focal length lens

The medium focus lens is similar to what we call a "pan-tilt", and the shooting effect is similar to what our eyes see. The focusing effect of this focal profile is very rich, and the large aperture effect is almost uniform. The coverage of the middle focus is about 35~85mm, and the visual field and visual angle are close to the human eye, so the pictures taken by using some of its focal segments will be closer to those seen by our human eyes, which is almost "what you see is what you get".

Features: Large aperture can create beautiful scattered scenes.

Because the medium-focus lens is a kind of fixed-focus lens, its aperture is the largest in the large aperture, and the large aperture is also very useful for blurring the foreground and background, which is conducive to creating a beautiful shooting effect.

Extended data

Product selection guide

The TV monitoring system can directly watch what happens in the monitoring place and target on the monitor through remote control of cameras, lenses, electric pan-tilt and other equipment. And transmit the image information content of the monitored place and target to a video recorder for recording.

Lens: Focus the light image of the monitored object on the target surface of a camera or CCD (Charge Coupled Device) sensor to produce a clear image of the monitored object on the target surface of the camera or CCD sensor.

When choosing a lens, the lens should be consistent with the industrial interface of the camera. The lens specification should be consistent with the camera target specification. The focal length of the lens should be determined according to the size of the field of view and the distance between the lens and the monitoring target. Except for the antimony sulfide camera tube, when the illuminance of the monitored object changes, the lens with adjustable aperture should be used.

When remote control is needed, you can choose a remote control lens device with optical focusing, aperture opening and zoom. When the camera needs to be hidden, it can be set on the ceiling or wall, and the lens can be pinhole or prism lens.

Lens: It can be divided into fixed focal length lens, zoom lens and wide-angle lens.

1, the fixed focus lens is used to capture fixed targets.

2. The zoom lens is used to take various pictures.

3. Wide-angle lens is used to take photos with small visual range and large viewing angle.

The selection of camera lens shall meet the following requirements:

① The focal length of the lens should be determined according to the size of the field of view and the distance of the lens target.

When shooting a fixed monitoring target, you can choose a fixed focus lens; When the viewing distance is small and the viewing angle is large, you can choose a wide-angle lens; When the line of sight is large, you can choose the telescope head; When it is necessary to change the visual angle of the monitoring target or the visual angle range is large, it is advisable to choose a zoom lens.

② When remote control is needed, you can choose a remote control lens device with optical focusing, aperture opening and zoom.