I am wondering about the CFe A vs B cards. CFe A cards in the A7siii is fine as it doesn't have the high bandwidth that the R5 does.
CFe B cards are relatively available in the market compared to CFe A cards.
CFe B cards are cheaper - at least last time I checked
CFe B cards have a higher bandwidth as they have 2 PCIe lanes vs 1 on the CFe A cards
=> CFe B = top 2GB/s vs CFe A cards @ 1GB/S
Canon have always formally qualified the higher write speed CFe B cards/OEMs which have generally been the larger card capacities although my 128GB Sony Tough has 1440MB/s write speed
From testing by The Digital Picture, the R5 has buffer depth of shots and seconds of shooting as:
20 fps RAW > CFexpress | 146 | 7.3 |
20 fps RAW > SD | 110 | 5.5 |
8k/raw DCI and 4K120 can only write to the CFe B card without any cinema compression without using the buffer.
It will be interesting what the CFe A cards can achieve in the A1