Optical lens basics (II)
ii. Points on focal length
Divided by the size of the field of view: small field of view lens, ordinary lens (about 50 degrees), wide-angle lens and extra wide-angle lens (100-120 degrees)
1.standard lens
the angle of view is about 50 degrees, which is also the angle that a person can see with his head and eyes not rotating. The focal length of a 35mm camera’s standard lens is mostly 40mm, 50mm or 55mm. The standard focal length of 120 cameras is mostly 80mm or 75mm. The larger the CCD chip, the longer the focal length of the standard lens.
2. Wide-angle lens
The angle of view is more than 90 degrees, which is suitable for shooting close-range and large-scale scenes, and can intentionally exaggerate the foregroundexpresses a strong sense of distance or perspective.
3. Long focal length lens
suitable for shooting long-distance scenes. The small depth of field can easily make the background blurred subject stand out, but the volume is bulky.
4. Reflective telescope lens
It is another super telescope lens design. It uses a mirror surface to form an image.B ut it is impossible to set the aperture, only the shutter can be used to adjust the exposure.
5. Macro lens (marcolens)
In addition to macro photography for very close range, and you can also telephoto.
iii. Interface type to divide
- C type /C-Mount lens
Flange focal length is the distance from the mounting flange to the convergence point of the parallel light incident on the lens. The flange focal length is 17.526mm or 0.690in. Rib installation: 1in diameter, 32 teeth.in. The lens can be used with a linear array sensor with a length of 0.512in (13mm). However, due to geometric distortion and market angle characteristics, it is necessary to discriminate whether the short-focus lens is suitable for use.
c mount cs mount adapter
- CS type/ CS-Mountlens
With a 5mm adapter ring, a C lens can be used on a CS-mount camera.
- U type lens
A variable focal length lens with a flange focal length of 47.526mm or 1.7913in and a rib mount of M42 × 1. It is mainly designed for 35mm photo applications (such as various domestic and imported 135 camera lenses), which can be used for any array with a length less than 1.25in (38.1mm).
- special lens
Such as the microscope magnification system. Pay special attention to the difference between CS and C. When different types of cameras and different types of Lens are connected, custom adapter rings are required. It’s expensive abroad.
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