NIKON AF-S TELECONVERTER TC-17E II
1.7× rear teleconverter for Nikon F
JP 2005-107261 A, Example 5 — Naoko Fukuda, Akiko Furuta
7 ELEMENTS / 4 GROUPS | 1.7× REAR CONVERTER | ALL SPHERICAL
A dedicated converter: it mounts only on lenses made to accept it. A teleconverter has no aperture stop of its own, so it is shown attached to a host lens, where the lens's stop stays the system stop and the focal length and f-number both grow by the converter's factor.