CF vs SD cards and write speeds

[KarlKrueger]

I recently bought a 5D Mark IV, I first put in a SD card I received from B&H (Sandisk Extreme - 40Mb/sec write speed). I always shoot RAW plus large JPEG. When shooting at 1/1500 sec the buffer filled up after 8 shots. I then put in another card I had (Sandisk Extreme Pro - 90 MB/sec write speed) and did the same test. This time it took 12 shots to fill the buffer. Clearly the faster card is better when you want continuous shots.

I'm asking if anyone has had experience with the faster compact flash cards. You can get them to go about 150 MB/sec write speed. Has anyone noticed a marked improvement of a CF card with those specifications vs the fastest SD cards. I don't think there is a faster UHS-1 SD card than the one I tried. UHS-2 will go up to 300 MB/sec but they are not compatible with this camera.

[Peter]

5DIII (5Ds included I guess) and its CF slot has in benchmark a maximum write speed of ~120 MB/s (Komputerbay/Lexar/Sandisk).  Average write speed of the 5Ds is ~101 MB/s.

5DIV has an average write speed of ~112MB/s.

The limit of CF interface: ¨~160 MB/s read speed and ~150 write speed. 5DIV should have a maximum write speed of ~130-140MB/s.

The SD slot in 5DIV has an average speed of 79 MB/s. Maximum write speed should be ~90-95 MB/s.

[KarlKrueger]

Thank you Peter. So the CF card should perform at about 40% faster write speed.

[Peter]

CF in a Canon is a lot faster than SD, yes.

I don´t know why Canon doesn´t upgrade the SD slot. Sony A9 has SD slots with an average write speed of 152 MB/s. Maximum write speed should be ~170MB/s.