This set is a fast for its focal lengths (respectively), allowing for hand-held photography under difficult lighting conditions. The lenses are crafted in Germany and incorporates a very complex optical design using "exotic optical materials such as barium dense flint with a high refractive index and fluor crown with anomalous partial dispersion."
"It uses aspheric lens elements and an internal focus mechanism for distortion-free images and consistent performance over the whole frame and across the entire focusing range".
Bottom line, Zeiss glass is crafted with gear and engineering ingenuity to give you top-level performance. This particular family of lenses are small, compact but sharp.