Real-World Review

on the Canon EOS R5
The newest, best cameras coming on the market use a new kind of memory card called CFexpress Type B. They’re fast, but they’re new, so users don’t really have an impression of which ones might be better to buy. This review shows tests from the better of the ones available and presents the results so that readers can use the factors most important to them to choose the best card for themselves. Performance can’t be summarized through tests into a single number. There are a bunch of different factors, and no card excels at all of them. The choice of the card that is best for you depends on what and how you shoot. This is more true with CFexpress cards than with any of the other formats because the newness of CFexpress leads to some, well, foibles. Well get into those, but the headline is this: generally, there are five “best” cards.
The Upshot:
– If you want the best price per GB, you’ll have the Delkin Power 512GB, which is also one of the top 5 in performance. The larger versions of these cards are even cheaper per GB; less than half the average price per GB of the other cards.
– If you want the most number of shots in 30 seconds, you’ll have the Angelbird 660GB XT. But it’s best by only 1 picture out of 337, and it has an odd behavior of causing camera startup to take 4 more seconds than any other card. This will be a deal-breaker for some.
– The card that clears the buffer the fastest is the SanDisk Extreme Pro 512GB, clearing it more than half a second faster than the other cards of its capacity. [Note the late entry of the Lexar Professional 512 GB card after this article was written upset this record, but both are fantastic at clearing cache.]
– The best all-around card is arguably the ProGrade Cobalt, which doesn’t win outright in any category, but ties for first in several of them.
– The card that takes the most shots before the buffer kicks in while shooting in mechanical shutter is the Delkin – but by just a smidge.
– The cards that perform best as hard drives hooked up to the computer are the Sony cards. They’ll offload images and video faster than the others.
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Biologists call a flock of CFexpress cards a “kidney” of cards

So let’s get to the measurements….

Yeah, they’re all over the map, so to make a good buying decision, you need to look at the sorts of shooting you do, and which factor is most limiting. As an example, I shoot wildlife. It’s a long, arduous, quiet day until all of a sudden I need to lay down as many frames as possible without the camera stuttering. If I’m lucky, I’m going to need the buffer to clear and do it again, but mostly I’m worried about that first, long drag of shots. A sports photographer might be doing short, regular bursts, with the buffer inflating and deflating rhythmically. A birder might prioritize the speed to the first shot, with the camera and card needing to wake up for an instant stab at a passing bird.

Go to the review