Yes, the Canon EOS R5 Mark II works with the Samsung PRO Plus 256GB SD — but only 4K-UHD Fine Standard LGOP (29.97/25/24/23.98fps) via the SD slot supported.
Samsung PRO Plus is UHS-I, rated UHS Speed Class 3 (U3) per Samsung's own spec page. Canon R5 Mark II's codec table requires only U3 on the SD slot for Standard LGOP 4K-UHD Fine recording; higher-bitrate Intra/V60/V90 modes require CFexpress. Card meets the SD-slot floor for that mode -- corrected 2026-06-21, previous verdict ("UHS-I cards will not record 4K at any framerate") was never sourced and contradicted Canon's own manual.
Conditions for compatibility
4K-UHD Fine Standard LGOP (29.97/25/24/23.98fps) via the SD slot supported -- card meets the UHS Speed Class 3 (U3) floor for that mode. 4K60 (Video Speed Class V60) and 4K120 (V90), and all CFexpress-only Intra/RAW modes, are not supported -- card is U3/V30, not V60/V90.
“Standard LGOP 29.97 CFexpress 2.0 U3 25.00 24.00 23.98”
Last verified:
Confidence: inferred