2 aspherical, 1 fluorite-like dispersion, 1 extra low dispersion, 2 super low dispersion
In most respects can deliver great image quality even when shooting wide-open. Although there are issues with ghosting and cat's eye, in many situations you'll be able to work around these. And while it's perhaps a tad front-heavy on smaller bodies, handling is otherwise excellent. We're fans of the lockable aperture ring, silky-smooth focus ring [...] A bigger concern is the Sigma's modest autofocus performance, especially when compared to Sony's GM lens.