Sigma's has been known the world over for their innovative design, ease of
use and for the excellent results that their zoom lenses produce - this
offering is no exception. The new 70-200mm f2.8 EX APO IF HSM lens features
an apochromatic optical design and four elements composed of Special Low
Dispersion (SLD) glass for high image contrast, resolution and color
saturation. For optimum performance in just about any photographic
situation, an internal focusing system means that the front barrel does not
rotate during focusing. For stability and the use of specialty filters, This
internal focusing system is a must. The internal zooming mechanism allows
the lens length to remain constant during zooming. Sigma's new Hyper Sonic
Motors (H.S.M.) provide silent, responsive autofocus action with both Canon
and Nikon AF SLR cameras. The H.S.M. feature also permits manual adjustment
of focus without the necessity of switching off the autofocus function.. The
Focus Free mechanism keeps the manual focus ring from spinning when the
camera is auto-focusing. The 70-200mm f2.8 EX APO IF HSM is fully compatible
with both the Sigma AF 1.4X and 2X APO EX Tele-converters. The new dedicated
1.4x APO Tele-converter features a high performance 5 element/3 group
optical design, and it is optimized for use with long telephoto and tele-zoom lenses.
