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One-Touch Focus Clutch Mechanism
The newly improved one-touch focus clutch allows the focus to be moved
quickly and easily from the AF position back into the MF position. In Nikon
and Canon mounts, the lens can be set for manual focusing without an
AF/MF switch or setting the body to the AF position.
Auto Focus Manual Focus
Internal Focus System
The two main methods of lens focusing are either the complete straight forward
movement of elements (used mainly with single focal length lenses), or the
rotation of the entire front lens barrel group (used mainly with zoom lenses).
The internal focusing system used by Tokina moves each lens group, but does
not change the overall length of the lens - this is especially useful with
telephoto designs.
The internal focusing system has a number of advantages, including:
1. Faster focusing
2. Improved handling due to fewer movements near the center of gravity
3. More compact lens designs
4. Superior use of filters as the front filter thread does not rotate
TECHNOLOGY - MECHANICAL
Standard lenses are made from a combination of spherical lens elements.
However, there can be problems with such lenses when light entering at the
edges of the lens may not be perfectly focused at the same point as light
entering at the center. That presents limits to performance in wide aperture
and super wide-angle lenses.Tokina uses aspherical glass elements in many
of its lenses. In addition to correcting spherical aberration, these lenses fully
correct light quantity and distortion at the edge of the image and provide
excellent results when used in combination with floating elements. Through
technical cooperation with Hoya, Tokina has succeeded in producing high quality
molded glass elements with a greater aspherical shape than any other lens so far.
This technique is unparalleled in its technological sophistication and excellence.
Aspherical Optics
SD (Super Low Dispersion) Glass
Lenses with the SD mark use Super-low Dispersion glass which minimizes the
secondary spectrum caused by chromatic aberration. Basically, these lenses
use FK01 and FK02 optical materials which gives them SD (APO) qualities.
This provides excellent image quality in telephoto lenses of 200mm or more
by correcting color aberration across the entire picture and bringing all colors
into focus accurately at the film plane.
TECHNOLOGY - MECHANICAL
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