Retrofocus-type (wideangle) lens
It is a lens which has the principal point behind the rear part of the entire lens.
The design is like the reverse of a telephoto lens (thus called "retro"), and since the back focus (back focal distance) can be obtained longer than the focal length, it is used mostly for SLR wideangle lens.
Compared to symmetrical wideangle lens, the brightness of the edge of the image field is great, but the distortion is bigger.
From the outside, the front lens element is large, and when looking at the aperture blade from the rear of the lens, the aperture blade appears larger when seen from the front.
Оттуда же. Так что я формально неправ наполовину - на зеркалках ретрофокусные ширики бывают, но на дальномерках их большинство.
