Autofocus, set up right
How do you set up autofocus and subject detection on a Nikon Z50 II — and when does Nikon's own guide warn that detection will dip?
AF-C for movers, AF-S for stills
AF-C keeps adjusting focus while focus is held active — the mode for people, animals and anything alive. AF-S locks once and holds it: landscapes, still life, posed work. AF-A, offered on this body, uses AF-S for stationary subjects and switches to AF-C when the subject moves. Video uses AF-F. For speed: continuous high runs about 5.6 fps on the mechanical shutter, continuous high (extended) about 11 fps, and high-speed frame capture + records at 15 or 30 fps with Pre-Release Capture (Custom Setting d3) keeping frames from before the full press.
Name the subject
The detection choices are Auto, People, Animal, Birds, Vehicle, Airplanes, and Subject detection off, chosen separately for photo and video. Animal means a dog, cat or bird; Birds is a dedicated category of its own. Vehicle is one bucket — cars, motorcycles, trains, airplanes and bicycles — while the separate Airplanes choice reads the aircraft itself. People and Birds get a face border, then an eye focus point. The guide cautions that subject-detection performance may drop during high-speed frame capture +, with HLG selected for tone mode, and in HLG or N-Log video.
Wide-area AF (C1) — a zone you size
Subject detection runs in Wide-area AF (S), Wide-area AF (L), Wide-area AF (C1), Wide-area AF (C2), 3D-tracking and Auto-area AF — not in Single-point, Pinpoint or Dynamic-area AF. Pinpoint and 3D-tracking are photo-mode only; video gets Subject-tracking AF instead. The C1/C2 zones are sized by the photographer with the arrow keys when the mode is selected. Size the zone to the subject — a head-and-shoulders box for portraits — and use 3D-tracking for subjects crossing the whole frame.
Detection with manual focus
With a manual-focus lens mounted, set MF subject detection area to All and the camera keeps detecting the chosen subject class across the whole frame, placing a focus point over it — over the eye for People — while you focus by hand. Wide (S) and Wide (L) limit detection to the current focus area. It is the feature that makes adapted vintage glass practical on this body. For animal and bird work, the guide advises switching the built-in AF-assist illuminator off (Custom Setting a11) — its light can trouble their eyes.
Set AF-C, People detection and a head-and-shoulders C1 zone, and track a person across the room. Then fit a manual lens, set MF subject detection area to All, and focus by hand while the camera marks the eye.