With the introduction of new firmware (V1.50), Fringer EF-FX smart adapters' AF-C tracking performance improved on following lenses: EF100-400/3.5-5.6L IS II and EF70-200/2.8L IS II.
Watch this video: (Please switch to 4K mode if possible)
For Fringer EF-FX Pro adapter users, you may visit my website to download the new firmware and its release notes to upgrade your adapter.
For Users who pre-ordered EF-FX Pro on 3/20, your adapter has already installed with firmware V1.50. Thus, you don't need to upgrade it. It has been sent to the international express service agent the day before yesterday and will be shipped to you through expedited service before April 1st. I'll let you know the tracking number once it's available.
Last round of pre-order took less than 48 hours to empty my stock. If you are interested in this product, please wait for the next round which may be open in late April. I'll send you a email at that time if you have left a message to me on my website. Thanks.