Description This high performance telemacro lens can focus from infinity to full 1:1 Life-size reproduction without accessories. At 1:1 reproduction the distance from subject to film plane is 18.1 inches, making this lens convenient for photographing subjects which are not easily approached, such as small animals or insects, etc. The apochromatic design and two SLD (Special Low Dispersion) glass elements, plus floating inner focus system effectively control Chromatic and Spherical Aberrations as well as Astigmatism, providing superb performance throughout the focusing range. The models for Sigma, Canon and Nikon AF cameras employ Sigma's HSM (Hyper Sonic Motor) for quiet, responsive AF function plus "full time" manual focus. A Focus Limiter switch aids in faster AF for closer or more distant subject situations, by restiricting the movement of the focusing mechanism. The HSM model lenses can be used with Sigma's 1.4X EX teleconverter as a 252mm f/4.9 lens, with SIgma, Canon and Nikon AF cameras, providing AF function from infinity to about 47 inches. At closer distances, the lens automatically switches to manual focus. (The models for Minolta and Pentax cameras will be manual focus with the 1.4X EX teleconverter.) This lens can also be used with Sigma's 2X EX teleconverter as a 360mm f/7 lens, for manual focus in all cases.