Internal Focusing System - Internal lens elements move when focusing, so the overall length does not change, creating a lens that focuses more quickly and doesn't change balance.
Aspherical Lens Elements - Three aspherical elements correct visual aberrations more effectively across the entire zoom range and help reduce weight.
ED (Extra-low Dispersion) Glass - Two ED Glass lenses minimize flare and greatly reduce chromatic aberration, giving you sharp, clear shots even at full telephoto extension.
Circular Aperture - Because aperture blades form a near circle at the wide openings used for low-light shots, spot-light sources have a pleasing circular defocused effect.
Advisory when using DT lenses with full-frame (35mm equivalent) DSLR cameras.
Sony a (alpha) lenses with the Digital Technology (DT) designation are ideal for use on APS-C size DSLR cameras and are not recommended for use with full frame DSLR camera bodies (such as the DSLR-A900). Although DT lenses can be used with full frame cameras, they can only realize a maximum of 11MP image size (when using the DSLR-A900), and are not guaranteed to provide accurate Auto Exposure performance.