Explanation:
1. What is wide angle: in the 35 mm film era the standard lens is about 50 mm, which is similar to the human eye angle of view, so called "standard" lens.
2. A value greater than this is often referred to as focal length, and a value smaller than this is referred to as angle.
3. The general common terms of address and approximate correspondence are as follows:
|
Focal Length
|
Angle
|
Name
|
|
17 mm
|
180°
|
Fish eye
|
|
21 mm
|
90°
|
Ultra wide angle
|
|
28 mm
|
74°
|
Wide angle
|
|
35 mm
|
62°
|
Quasi wide angle
|
|
50 mm
|
47°
|
Standard
|
|
85 mm
|
28°
|
Medium focal length
|
|
105 mm
|
23°
|
Medium focal length
|
|
135 mm
|
18°
|
Medium focal length
|
|
200 mm
|
12°
|
Long focal length
|
|
300 mm
|
8°
|
Super telephoto
|