Carl Zeiss T* (T-star) coating
Coated optics were pioneered by Carl Zeiss -- and this superb lens features the Carl Zeiss T* (T-Star) coating that virtually eliminates lens flare, internal reflection and light scattering that can otherwise occur at glass-to-air surfaces. The T* coating contributes to outstanding image quality, with high contrast and uniformly excellent resolution right out to the image edges. Not simply applied to any lens -- the T* symbol only appears on multi-element lenses in which the required performance has been achieved throughout the entire opyical path, therefore guaranteeing the highest quality.
Focus hold button
Once you've adjusted focus to where you want it, pressing this button on the lens barrel will keep the lens locked to that focusing distance. The preview function can also be assigned to this button through the camera's custom settings.
Rear focusing elements
Only the rear groups of the opyical system move to focus the lens, which allows for speedy AF operation and a shorter minimum focusing distance. Since the front of the lens does not rotate, operability is improved when shooting with a polarizing filter attached.
SSM (Super Sonic wave Motor)
SSM is a piezoelectric motor that contributes to smooth and silent AF operation. The mootr produces high torque at slow rotation, and provides immediate start and stop responses. It is also extremely quiet, which helps keep autofocusing silent. Lenses that feature SSM also include a position-sensitive detector to directly detect the amount of lens rotation, a factor that improves AF precision overall.
Carl Zeiss Planar Lens
The Carl Zeiss Planar lens first became synonymous with high-performance lenses by realizing a large aperture, flat reproduction characteristics, and the successful removal of astigmatism. Once the T* coating was introduced to dramatically reduce internal reflection from its progressive double Gauss design (with front-back symmetry), Planar became one of the most renowned lenses in the Carl Zeiss lineup, which is synonymous with high-performances standard lenses.
ED (Extra-low Dispersion) Glass
Because light of different wavelength (or color) bends at different angles when it passes through a lens, ED Glass is used in all Carl Zeiss lenses to eliminate chromatic aberration by correcting certain wavelengths of light for sharp, clear images with well-defined colors.