Yes, the Lexar Professional 1667x 64GB SD is compatible with the Sony FX3.
Lexar 1667x is UHS-II V60. Sony FX3 spec table requires V60 minimum for XAVC S 4K via SD slot and V90 for XAVC S-I 4K. Card meets V60 for XAVC S modes; falls short of V90 for S-I intra-frame recording.
Limitation
Cannot record XAVC S-I 4K (intra-frame, up to 1200 Mbps in S&Q mode) -- requires Video Speed Class V90 per Sony's own spec, this card is V60. Works for XAVC HS/S 4K (V60 required, met) via the SD slot -- FX3's SD slot supports up to V60-tier 4K directly, no CFexpress required for standard modes.
“Sony FX3 Help Guide: XAVC S 4K at 280Mbps requires SDXC V60 or higher; XAVC S-I 4K at 600Mbps requires SDXC V90 or higher — V60 card supports standard 4K but not intra-frame 4K.”
“Faster Video Capture With V60 Class For Professional Users”
Last verified:
Confidence: inferred