Autofocus
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Autofocus

Both cameras provide autofocus using on-sensor phase-detect autofocus systems. The Z7 features 493 phase-detect AF points with an impressive 90% horizontal and vertical coverage of the frame. It also features face detection technology plus body movement (designed to continue tracking a subject even if they turn their face away from the camera), and is rated down to -1EV with an F2 lens attached (-4 EV if you enable 'Low Light AF', albeit at the cost of much slower autofocus). Nikon also gets credit for its bright AF points which are easy to see in the viewfinder, compared to Sony's grey AF points that can be difficult to see against, well, most backgrounds.

The a7R III has 399 phase-detect AF points, which cover a smaller area of the frame than the Nikon, but it also utilizes 425 contrast-detect AF points to provide greater coverage. It also includes Sony's very effective 'Eye AF' system, one of our favorite features on the camera. Using Eye AF, the a7R III identifies and focuses on a subject's eye, tracking it tenaciously if it moves within the frame. The Z7 doesn't offer an Eye AF mode. The a7R III is rated to focus, with F2 lenses, at lower light levels than the Nikon (outside of Nikon's 'Low Light AF' mode): an impressive -3EV in fact.

Although Nikon did a good job of translating its DSLR user experience to a mirrorless camera, one feature that didn't make the transition is its 3D Autofocus system, which we consider best-in-class. Instead, the Z7 inherits a version of the AF system used by Nikon's DSLRs in live view mode. Instead of simply placing an AF point over your subject and initiating focus, the Z7 requires you to press OK to enable subject tracking, and to press it again to change subjects. By comparison, Sony's Lock-on AF provides a more seamless experience for subject tracking: like Nikon DSLR 3D Tracking, you simply place your AF point over your subject and half-press to initiate tracking. Eye AF even works in a similar way. This simple method of quickly selecting your subject on the fly is, sadly, completely missing from Nikon's debut mirrorless, and that will undoubtedly impact fast-paced shooting with high demands on AF performance.

Overall, the a7R III wins here, despite the fact that Nikon has one of the best AF systems on the market in its DSLRs. If it can bring that system, or something similar, to its mirrorless cameras it may well change the equation.