Is there a reason lenses split 18-55mm and 55-200mm?

Started Apr 26, 2013 | Discussions thread
Klipsen Veteran Member • Posts: 6,155
Tele lenses and wideangle lenses are opposite constructions

Wideangle lenses are usually of retrofocus design, i.e. a "telelens facing the wrong direction". This is because otherwise there's not enough room for a mirror.

Obviously, it's very difficult to make a lens that faces both in the right and the wrong direction using a single bayonet, but by splitting the focal range in two, things become a lot easier.

Also, the position of the diaphragm determines whether distortion is barrel or pincushion shaped. Only if the diaphragm is at the optical centre will distortion be nil. On a zoom it is impossible to have no distortion - except, possibly, at one focal length - and the wider the zoom range, the greater the distortion. This is evidenced by the distortion figures for super zooms.

 Klipsen's gear list:Klipsen's gear list
Sony Alpha DSLR-A700 Sony Alpha DSLR-A900 Sony Alpha NEX-7 Sony E 18-55mm F3.5-5.6 OSS Sony 70-200mm F2.8 G +18 more
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