Autofocus & Burst
The Z5 focus system is very similar to the Z6, it also inherits a lot of the good from the D750 (remember similar sensor). Nikon uses phase-detect pixels on the sensor that can provide both focus and exposure information. The Z5 has 273 selectable points for autofocus, but there are thousands of points on the sensor via the phase detect sensor.
The Z5 focuses very well in good light, with results similar to the D750. It is not a great low light focusing camera though. Normal focus performance extends to -2 EV (extends to -3 EV) versus -3.5 EV on the Z6 (extends to -6 EV).
The benefit of the Z cameras is Nikon is committed to firmware updates and updates can be used to improve the AF performance.
The Z5 is a slow camera when it comes to burst rate. It can only 4.5fps, which is WAY below what other mirrorless cameras in the price range are capable of, and below the 12fps of the Z6. It’s interesting that Nikon couldn’t offer a better burst rate with the Z5.
Nikon uses rows of phase detect photosite masking on the Z5 sensor. The photosites on those rows can provide both focus and exposure information. Basically, every twelfth row has this dual-function nature. Nikon claims 273 points for autofocus, but that’s selectable single points using the camera controls. In reality, there are thousands of autofocus points in the camera, as is true of most mirrorless cameras using phase detect on the sensor. One thing, though: none of these autofocus detection sites are cross-type, as you find in the DSLRs. That means that focus is more responsive to detail on one axis only (long axis).
Video
In my opinion, the video features are a little disappointing. But, you can’t have it all in a $1,000 body. Nikon definitely placed the emphasis on stills, and the Z5 shines for still photography, but video leaves a lot to desire.
The Z 5 supports UHD 4K video recording at up to 30 fps and Full HD recording at up to 60 fps. The kicker is 4K video gets a massive 1.7x crop slapped on it. There are no modes above 60fps for super slow-motion video. It also cannot record 10-bit video, or N-Log/ProRes Raw, even when an external recorder is used.
I can’t figure out why, but it doesn’t have a fully articulating LCD (neither do the Z6/Z6 II). Other options do, and having that full articulation can make a huge difference when recording video.
The video quality is still good, and bit rates are similar to other cameras priced the same. I think the biggest deal for video is the 1.7x crop.