Lens Construction: 17 elements in 12 groups (4 aspherical elements)
Each piece of glass is made as thin as possible while employing glasses with a high refractive index and four aspherical lenses. The high level of production technology at SIGMA’s only manufacturing base, the Aizu factory, provides the exacting precision necessary for processing these thin glass elements and making this mass production possible. In addition, the floating focus construction ensures high performance while shortening the overall length, resulting in a compact lens. In the mechanical design phase, emphasis was placed on weight reduction. Through the systematic elimination of individual components, SIGMA attained the distinction of producing the lightest lens in its class, weighing a mere 745g / 26.3oz.*
* These figures are for L-Mount.