The SIGMA 18-50mm F2.8 DC DN | Contemporary For Sony E Mount Cameras is remarkably compact, matching the portability of APS-C mirrorless camera bodies. This makes it a perfect workhorse lens that is ideal for general day-to-day use. The lens is currently the smallest and lightest in its class (at time of writing), boasting a maximum diameter of 65.4mm, a length of 74.5mm and weight of 290g (L-Mount version), yet still maintains a constant aperture of F2.8.
To keep the lens as light as possible, SIGMA constructed the body from carefully selected materials. A polycarbonate called Thermally Stable Composite (TSC) was used for the construction of the barrel, which is sleek, robust, and importantly has a thermal conductivity close to that of aluminium. This ensures stable performance and good operability when used in changing temperatures.
By using metal for some of the internal structure, the parts could be much thinner and have a higher rigidity, ensuring the lens can stand up to frequent, heavy use.