First, know the lens logo

1. hood (to prevent glare and lens collision).

2. Focus ring (adjust the focus position of the lens).

3.AF/MF focus switch (auto/manual focus switch).

4. Zoom ring (adjust the focal length of lens).

5. Current focal length (corresponding number is current focal length).

6. Lens back cover (lens protection/dustproof).

Second, the lens classification

Zoom lens is a kind of lens whose focal length can be changed in a certain range, and it has multiple fields of view.

A fixed-focus lens has only one fixed focal length, only one focal length and only one field of view.

Classification of focal lengths: super wide-angle lens with focal length less than 20mm, wide-angle lens with focal length of 2 1mm-40mm, standard lens with focal length of 4 1mm-60mm, medium-focus lens with focal length of 61mm-0/00mm, and focal length of/kloc-0.

Thirdly, the influence of focal length on visual field.

Focal length and field of view: the smaller the focal length, the wider the field of view, and the larger the focal length, the narrower the field of view.