Andy Westlake tries out Sony's latest premium fast prime designed for Alpha 7 users, the Sony Planar T* FE 50mm f/1.4 ZA
Sony Planar T* FE 50mm f/1.4 ZA review – Focusing
Focusing employs a ring-type ultrasonic motor to drive the large and heavy focus group, with auto or manual focus selected by a switch on the side of the barrel. On the Alpha 7R II, I found autofocus to be quiet but not especially fast, with a very noticeable ‘wobble’ back and forwards before settling on the subject. Focus speed also slows down progressively as you choose smaller apertures, especially in marginal light, due to Sony’s habit of always stopping the lens down to the taking aperture for focusing. Crucially, though, AF was consistently accurate, even when shooting off-centre subjects with the aperture wide open. This reliability is typical of mirrorless systems, which always use the main image sensor to determine correct focus, and is not necessarily always matched by DSLRs.
Manual focus is by wire, with the smoothly rotating focus ring used to drive the AF motor, rather than being mechanically coupled to the focus group. This isn’t necessarily the most tactile means of focusing, but it works well enough and is very accurate, especially as turning the focus ring will automatically switch the viewfinder to magnified view. But I really can’t see why Sony couldn’t have used a design similar to the FE 90mm f/2.8 Macro, where pulling the focus ring towards the camera effectively emulates an old manual-focus lens, with a distance scale and hard end-stops at the ends of its travel. It would be far more fitting to a lens of this price.