Recently I rented a EF600/4L II and had it optimized. To my surprise it works incredibly well on X-T3 when doing AF-C tracking.
![broken image](http://custom-images.strikinglycdn.com/res/hrscywv4p/image/upload/c_limit,fl_lossy,h_9000,w_1200,f_auto,q_auto/975448/DSCF8657s_mssrar.jpg)
I set X-T3 to AF-C mode, CH (11 fps) and Face/Eye detection on. The focusing object is a person riding a electric motorcycle moving fast towards the camera.
![broken image](http://custom-images.strikinglycdn.com/res/hrscywv4p/image/upload/c_limit,fl_lossy,h_9000,w_1200,f_auto,q_auto/975448/DSCF8804s_qg4jpd.jpg)
30 pictures were taken in less than 3 seconds. The focus areas were cropped at 100% scale and combined to the following picture. (Click here to see in original size.)
![broken image](http://custom-images.strikinglycdn.com/res/hrscywv4p/image/upload/c_limit,fl_lossy,h_9000,w_1200,f_auto,q_auto/975448/crops_ujlslj.jpg)
I also tested video mode Face/Eye tracking. Thanks to the great improvements of PDAF performance and coverage of X-Trans IV CMOS, both still and video mode works very well.
Combined with the video clip recorded from the HDMI output while doing continuous shooting testing, I made a demo video.
The support for EF600/4L II would be added into the next version (V2.50) of Fringer EF-FX (Pro) adapters' firmware which is to be released soon.
Thanks!