Is this budget fast prime lens the perfect choice for Alpha 7 users? Andy Westlake finds out
Sony FE 50mm f/1.8 review: Focusing
One characteristic of the FE 50mm f/1.8 that has carried over from traditional manual-focus SLR lenses relates to focusing. Unlike more modern designs, which overwhelmingly employ high-speed internal focusing, the FE 50mm f/1.8 works by racking the entire optical unit back and forwards instead. Indeed, at its minimum focus distance of 0.45m, the front of the lens extends almost 1cm forward from its infinity position. This approach isn’t a problem for manual focusing, but turns out to be far from ideal for autofocus.
Indeed, when it comes to AF, this is probably the least satisfactory lens I’ve used for many a year. Even when used on the Alpha 7R II with its much-lauded on-chip phase-detection, autofocus is slow and often feels uncertain. The lens tends to noticeably overshoot the mark and readjust back to correct focus – behaviour that’s much more typical of a contrast-detection system. Because the focus motor has to move lots of glass around this isn’t a quick process, and I often found that I was held up for a second or two waiting for the lens to achieve focus. Video shooters will also find that the whirring of the DC motor is audible on their soundtrack.
With static subjects this sluggishness isn’t too detrimental to the picture-taking process, although it is rather irritating. Fortunately, focus accuracy is consistently high, just so long as you place the AF area on a reasonably high-contrast target. But when faced with trying to get a quick shot, it all-too-frequently fails to react in time. To provide some context, Canon’s recent EF 50mm f/1.8 STM also uses a unit-focus, double Gauss design but is noticeably quieter and quicker.
You can, of course, focus manually, using the broad, smoothly rotating ring on the barrel. This employs a focus-by-wire mechanism that instructs the lens’s internal motor to move the optical unit. Like most such systems, it allows very accurate focusing when used in concert with the camera’s focus aids, such as magnified and peaking views. But it’s not especially intuitive – for example, there’s no change in resistance when the focus reaches the end of its travel. To be fair, this is commonplace with CSC lenses, and you’ll only get more tactile manual focusing from rather pricier designs.