The Sigma 120-300mm F2.8 EX DG OS APO HSM (for Canon) is a unique lens in the photo industry. Its design is based around high speed superior optical performance. Created for Full Frame sensors, it may also be used with APS-C sized sensors as well. It has an array of technology to guarantee the highest level of image quality. This technology includes a Hyper Sonic Motor (HSM), an optical Stabilizer, Inner Focusing and Zooming System, SLD and FLD Glass Elements (FLD has a performance equal to fluorite). The HSM ensures quiet, high speed, accurate autofocusing while the OS allows for use of shutter speeds approximately 4 stops slower than would otherwise be possible. Super Multi-Layer coating reduces flare and ghosting working together with the SLD and FLD glass elements for maximum correction of chromatic aberrations. An Inner Focusing and Zooming system produces sharper images throughout the entire zoom range. With a large fixed aperture of F2.8 the 120-300 is capable of handling any lighting scenario.