[A full review of CFexpress cards compared against each other here.]
Camnostic rented a Nikon Z7 II for the express purpose of testing the increased throughput possible with the firmware that allows for the use of CFexpress cards. The upshot: throughput is improved by about a third. That’s pretty significant, and a good bit better than the mere 1/7th improvement found on the Panasonic bodies that were similarly enabled to shoot CFexpress. It still falls short of the Canon R5 CFexpress implementation, which allows for roughly twice as many shots in 30 seconds.
In the chart below, the blue lines indicate the number of frames put through the camera in 30 seconds. The better XQD cards would allow about 97 frames in that time. The best of the CFexpress cards, the Angelbird XT 660GB card, put through 173 RAW images, and the entire set of seven CFexpress cards averaged 129 frames, the 30 average percent boost.
The Sony card – originally the only one officially recognized as supported by Nikon – did well, with 146 frames, but did not prove to be the best.
As the Z series will be getting a firmware upgrade next week (preview here), some have expected more CFexpress card compatibility improvements, but these tests indicate that the bodies work with the format pretty well as is. There are speed bottlenecks relative to other implementations, but many observers have assumed this is due to hardware bus limitations rather than firmware limits. The graph above shows the light green lines indicating the speed with which the cache is cleared by the camera with the particular card brand. Because there does not seem to be a direct relationship between raw cache clearing capacity and the frames taken in 30 seconds, there does seem like there might be room for efficiencies to be maximized with some of the cards.