Os (Optical Stabilizer) functionSigma's Os (Optical Stabilizer) function uses sensors inside the lens to detect any motion, then moves specific lens elements in order to effectively minimize blur caused by such movement.OS2OS2 is the newly developed optical stabilizer algorithm. Compared to the previous algorithm used by Sigma lenses, OS2 improves the effect of optical stabilization significantly.Inner focus systemTo increase stability, this lens configuration uses movable internal lens elements that adjust focus without changing the length of the lens barrel.Compatible with Lens Aberration CorrectionMatching the optical characteristics of the lens, this function performs in-camera corrections of peripheral illumination, chromatic aberrations, distortion, and more, to further enhance image quality.hla (High-response Linear Actuator)Hla is Sigma's proprietary linear motor.