Autofocus (Adapted lenses)

One of the features of the a7R II that most caught our attention was the suggestion that the a7R II could offer near DSLR-standard autofocus when using other mount lenses - vastly extending the range of lenses that can be used robustly with the camera and opening up its utility as a second body or gateway to a new system. While previously one could adapt almost any lens to the system due to its short flange distance, manual focus or very slow, hunting-riddled contrast detect AF (CDAF) were the only options for focus. The a7R II is able to use its on-sensor phase detection AF (PDAF) with adapted lenses - a frankly unprecedented offering we'd always hoped for, but had stopped expecting.

At present, Sony makes an adaptor to use A mount lenses, while several manufacturers make adaptors for mounting Canon EF lenses. Adaptors for using Nikon F-mount lenses with electronic focus control are expected soon.

Benefits

Phase detection is very fast with most adapted lenses, near native speeds in most cases, but your results may vary depending on lens and adapter. Fredmiranda.com maintains a running list of lenses known to work well. You can use a Flexible Point to position your AF area anywhere in the frame and utilize all 399 phase-detect AF points with most adapted lenses (some lenses with extensive focus breathing can struggle). Wide AF area with subject tracking based off of depth information also works reliably, as you can see here, but the mode itself is of limited utility since the camera chooses your subject, not you. We were particularly pleased to see that face detection remains available, and makes for a convincing way to shoot human subjects with adapted lenses which, when paired with their own native bodies, often don't benefit from face detection. Only higher end, more recent DSLRs offer face detection in viewfinder shooting and, even then, are nowhere near as accurate at it as the a7R II, or any mirrorless camera for that matter (due to the inherently low resolution metering sensor DSLRs use for rudimentary subject recognition and tracking).

A key thing the camera retains with adapted lenses is the improved accuracy of focus that comes from its on-sensor focusing system. This is not to be underestimated: DSLRs require lens-specific calibration to correct the measurements the secondary PDAF sensor makes so that it's appropriate for the image sensor plane. And since DSLR PDAF sensors see through small virtual apertures looking at the outer peripheries of lenses, a correction factor must be included to account for residual spherical aberration of lenses. Ultimately, this means that, particularly with fast lenses, you cannot trust that every AF point to focus accurately, and even if you do 'microadjust' a body-lens combination yourself to correct for any front- or back-focus, that one global microadjustment value may not be appropriate for different AF points, different subject distances, different colored lighting, environmental factors such as temperature, etc. The a7R II does away with all of these concerns.

Limitations

The camera does not retain its full range of features when working with adapted lenses. The maximum shooting rate at which the camera can continuously focus drops from 5 fps to 3, but it's commendable that the camera does retain the ability to continuously AF at all. Unfortunately, Eye AF and the Lock-On AF area, along with Zone and Expand Flexible Point, are unavailable as AF area modes with adapted lenses. We really hope to see this change in future firmware or bodies, as some of these modes are fundamental to making the a7R II such a compelling photographic tool.

The other loss of function will only be expereinced when you're trying to shoot video: the camera drops to only using contrast detection AF with adapted lenses. This means that attempts to autofocus will include significant (and usually quite distracting) degrees of hunting, to the extent that we'd suggest manually focusing non-native lenses for video.

Autofocus performance (Adapted lenses)

Our first test was to see how well the Sony did at refocusing an adapted Canon 24mm F1.4 lens, as we walked towards our test chart.

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The performance is pretty good, with fairly consistent focus until the camera gets very close to the chart. The gap between images is also fairly consistent until the camera gets very close to the chart.

Canon EOS 5DS performance

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For means of comparison, we've shot the same test for our forthcoming Canon EOS 5DS review. This broadly bears-out our expectations: it isn't always perfectly in focus but it's fairly consistent, with several images showing signs of being noticeably front- or back-focused.

The other thing worth noting is that the Canon managed to shoot 26 images during its sequence, compared with 11 shots from the Sony. Both cameras were set to focus priority (only shooting when confident of focus), but the Sony seems to be more discerning than the Canon. Even taking into account its slower shooting rate with adapated lenses, you'd expect to get around 15 images in the time the Canon took to take 26. However, with the exception of the close-up images, the Sony seems to have been more determined to wait for perfect focus before shooting a shot, resulting in fewer mis-focused images.

We then re-conducted our cycling test, to confirm that the camera's performance is consistent when using a longer lens and re-focusing over greater distances.

Center autofocus

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The straight run at the camera, using the central autofocus point, produces reasonable results but not as good as those from using native lenses. Just as in the test above, of walking towards the test scene, you can see that the camera particularly struggles when the subject gets close to the camera.

Wide area autofocus

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The reduction of the camera's frame rate from 5 fps to 3 fps is noticeable but the hit-rate remains reasonably high. Despite not having access to the lock-on tracking mode (which we've already seen tends to get overwhelmed if you use it for continuous shooting), the camera makes a reasonable job of guessing what the subject is and keeping it in focus.

These results aren't suddenly going to let you go out and shoot professional sports (even if you could live with the limited shooting rate), but suggest that the camera will focus on the right thing if you're picking your moment to shoot each image.

Inconsistency

A warning note should be struck before you conclude that you can just buy an a7R II and adapter and expect this level of performance from third party lenses. Based on our experience with Canon lenses, we found work better than others, while some can't be used at all. In the case of EF lenses, it's not clear yet whether the list of best performance overlaps with the improved autofocus feedback system that Roger Cicala identified in Canon's most recent lenses (post ~2010).

At present Sony only makes adapters for its own A-mount lenses, which means introducing a third manufacturer into the equation (Sony, adapter manufacturer and lens maker). This means adding another link in the chain between the camera and the lens and an extra source of inconsistency. During our testing we got different results (specifically in terms of initial AF acquisition speed) depending on which adapter we used and what firmware version it was running - suggesting the adapter isn't playing a passive role in proceedings.

Overall we'd suggest that, if you're planning to buy an a7R II to use with lenses you already own, it's probably worth renting a body and testing your favorite lenses with it before committing yourself to a purchase.