What does telephoto lens mean?

A telephoto lens is a photographic lens whose focal length is longer than that of a standard lens. Telefocal 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 85 mm-300 mm is a normal telephoto lens, and the lens with a focal length of more than 300 mm is a super telephoto lens.

The telephoto lens is also called telephoto lens and telescope head. The focal length varies from 135-800mm, and some are even longer.

In the process of shooting distant objects, it is often found that you can't get close to the subject. This requires the use of telephoto lenses, which can well show the details of distant scenery and shoot some subjects that we are not easy to get close to.

The focusing lens has long focal length, small viewing angle and 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.

Type: telephoto lens can be divided into general telephoto lens, inverted telephoto lens and reflective telephoto lens according to the different optical group structures.

Features: Shooting with a long focal length lens has the following features:

Small viewing angle: therefore, the spatial range of the shooting scene is also small. Under the same shooting distance, the shot image is larger than the standard lens, which is suitable for shooting the details of distant scenes and shooting inaccessible subjects.

Short depth of field: therefore, you can highlight the subject in a messy environment. However, it brings some difficulties to accurate focus adjustment. If the focus is slightly inaccurate when shooting, the subject will be blurred.

Poor perspective effect: This kind of lens has obvious characteristics of compressing spatial depth distance and exaggerating background. When using a long focal length lens, it is usually used to shoot distant scenes. Due to the absorption of air and the influence of diffuse light, the contrast of the captured image is small, and the dust particle extinction is serious, so it is not easy to achieve very accurate focusing. When shooting with a telephoto lens over 300mm, it is difficult to focus all colors of light on one point, resulting in sub-spectral problems.