What are the advantages and disadvantages of periscope lenses compared to traditional telephoto lenses?

1, structure: periscope relative to the traditional telephoto, need to increase the reflective surface to bend the optical path of 90. this reflective surface can be a simple mirror or the use of total reflection prism, prism is relatively more commonly used.

2, the advantages of different: the first because of the telephoto module equivalent focal length is very long (generally more than 80mm, most in the 100mm equivalent or so), resulting in. If you want to control the thickness of the traditional structure, but do not want to sacrifice the equivalent focal length, then you can only use a small bottom (1/5.5" or so[1]) and periscope telephoto module because the optical path is bent 90 *, so the thickness of the module (Z-axis height) into length (X-axis length).

This allows the actual focal length to be longer while the Z-axis height remains the same. In other words, the base can be made larger with the same equivalent focal length: 1/3.4" or so, and more pixels can be made, or vice versa.

The advantage of a conventional telephoto: The advantage of a conventional telephoto is its simplicity. Since there is no need for prisms or other structures for reflection, traditional telephoto has less light loss and smaller module size. In addition, although the bottom of the periscope than traditional can be made bigger, but does not mean that the low light traditional telephoto is far worse, after all, traditional telephoto aperture is easier to make bigger.

The same equivalent aperture: 1/5.5" traditional telephoto is F26.43], while 1/3.4" periscope is F24.48, not counting the optical system loss of periscope into the amount of light is only 16% more, not to the first gear.