16-18-21 MM BAYONET MOUNT LENSES
It is important to note that Leica lenses had their focal lengths specified in millimeters from 1925 to 1928, in centimeters from 1928 to 1970, and again in millimeters from 1971 onwards360.
16-18-21 f/4 Tri-Elmar-M ASPH
The Leica 16-18-21 f/4 Tri-Elmar-M ASPH, introduced in 2008 at Photokina277, is the second lens to feature a zoom design with three mechanical slots for fixed focal lengths, with the first being the Leica 28-35-50 f/4 Tri-Elmar-M ASPH lens361. The lens has been designed to work equally well on analog and digital M cameras277.
The lens employs a linear movement that simplifies its design to some extent; however, the addition of internal focusing introduces mechanical complexity to an already intricate optical structure361. Its compactness is achieved through an innovative method of attaching a separate filter holder and lens hood361. This patented thread mechanism ensures that the hood and filter holder stop at a predetermined position, regardless of where you begin the movement, providing a secure lock and precise positioning similar to a bayonet mount361.
The lens is resistant to flare, and shooting directly into the sun generates minimal ghosting effects361. The lens was introduced during the production of the Leica M8 camera to offer users classic viewing angles at 21, 24, and 28 mm focal lengths361.
The Leica 16-18-21 f/4 Tri-Elmar-M ASPH identified by the catalog number 11642361. Its serial number starts from 3995091361. The lens consists of 10 elements arranged in 6 groups, including two elements with aspherical surfaces361. It offers an angle of view of 107º, 100º, and 92º, with a minimum focus distance of 50 cm361. Weighing 335 grams, it includes a filter holder size E67 and a filter holder/adapter (catalog number 14473)361. This lens is available only in a black anodized finish and features 6-bit lens identification, along with a screw-on type lens hood361.