This is just a simple table I set up to show my testing with different cards. Earlier Rob Galbraith did similar comparison, but he had lot of different cards and cameras to test. I'm only using equipment I have myself. His testing was done couple years ago, so the test for Canon 5D Mark III was done with the 1.0.7 firmware. My testing was done with the latest (as today) 1.2.3. Also Rob's testing he had the 1000x Lexar cards, whereas I was using the new version of 1066x cards.

I also could test SD cards, but for anyone interested on the buffer clearing speed, those are just too slow. I tried to use similar setup/settings as Rob, although it's not identical.

My settings: 5D Mark III with 24-105mm lens. Manual focus on the lens at a wall in my office. Camera on manual, 1/200 F5.0 ISO400, with high-speed fps mode (6fps), shooting RAW only, no jpeg.

I used intervalometer to press down the shutter for exactly 30 seconds. I recorded how many pictures the camera took in that time, and I also timed how many seconds it took to clear the buffer. This was done by visually looking at the card write LED on the camera body.

Each test case was repeated 3 times, and below the result is average of those 3. Cards were formatted in the camera between each test. All my old cards were cheapest I could buy, only the Lexars are fast CF cards.

Card name, size and speed	Pictures taken in 30 seconds	Time to flush the buffer (seconds)
Lexar Professional 1066x 64GB	137	3
Kingston Elite Pro 8 GB 133x	40	14
A-Data 4GB 120x	36	18
Patriot Signature 16 GB 266x	31	24

I repeated the same test with EOS 7D (Mark I) with FW 2.0.0.

Card name, size and speed	Pictures taken in 30 seconds	Time to flush the buffer (seconds)
Lexar Professional 1066x 64GB	120	6
Kingston Elite Pro 8 GB 133x	57	21
A-Data 4GB 120x	51	27
Patriot Signature 16 GB 266x	45	33

And last, I repeated the test with EOS 1DX with FW 2.0.7.

Card name, size and speed	Pictures taken in 30 seconds	Time to flush the buffer (seconds)
Lexar Professional 1066x 64GB	171	7
Kingston Elite Pro 8 GB 133x	71	33
A-Data 4GB 120x	65	42
Patriot Signature 16 GB 266x	59	53

Conlusion: Lexar is the fastest by far. The fact that it takes that many more compared to the others, and that it takes only 3 seconds to clear the buffer, means that it can almost keep up with the 5D3 fps rate even with full size RAW files. 1DX 12fps also was almost matched by the card writing speed, only 7 seconds to clear the buffer after taking amazing 171 photos is 30 seconds. For the other cards, it seems it doesn't matter what's the rated speed. The one which was supposed to be the fastest, performed the slowest.

But if you're not shooting sports or something similar which requires fast burst rates constantly, even the slow ones are good enough. For sports shooting, the Lexar is awesome. I used to have to be careful not shooting too fast or I hit the buffer limit. Now with the Lexars, my new problem is I end up with too many pictures.

If your wondering about the domain name, it was just old domain I happened to own and wasn't using, so it was easy to drop the comparison table here.