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These cards are of the same brand, both are type "SD HC", both also have the little 10 in a circle (which if I have understood things correctly is some measurement of the speed of the card). But the left card also says 90MB/s, has a "1" inside a "U", a Roman numeral "I", and says 600X.

I'm doing burst photography, and so would one of these be better for that than the other?

  • \$\begingroup\$ What camera? How many shots per burst? \$\endgroup\$
    – AthomSfere
    Commented Mar 29, 2017 at 22:22

3 Answers 3


While the information is incomplete on the card, it is the left one. Both are classified to Class 10 which is 10 MB/s. The other got UHS-1 which also means 10 MB/s, so nothing to distinguish them yet.

The hint that the left one is better are the 90 MB/s which we do not know if it refers to reading or writing speed. For burst shooting, what you need is a faster writing speed. A search online says that the card on the left writes at 22 MB/s. That's far from 90 MB/s but still twice as fast as 10 Mb/s for the other.

Standard SD cards can be made with a max capacity of up to 2GB.
SDHC cards come in capacities ranging from “greater than 2GB” to 32GB.
SDXC cards range from “greater than 32GB” to 2TB.

SD cards are classified with numerical speed classes. At present, there are 4 non-UHS Speed Classes and 1 UHS Speed Class in use. These ratings are based on a minimum sustained data writing speed.

Class 2:  2MB/s minimum write speed
Class 4: 4MB/s minimum write speed
Class 6: 6MB/s minimum write speed
Class 10: 10MB/s minimum write speed
UHS Speed Class 1 (UHS-I): 10MB/s minimum write speed

Note that the card type (SD, SDHC or SDXC) is different from the card speed class (Class 2, 4, 6, etc.).

Hope this is helpful

  • \$\begingroup\$ these cards are both labelled as SDHC class 10. \$\endgroup\$
    – Steve Ives
    Commented Feb 21, 2017 at 9:46
  • \$\begingroup\$ That is interesting, but doesn't address the question - is there are difference between the two he showed? \$\endgroup\$
    – Aganju
    Commented Feb 21, 2017 at 12:26
  • 1
    \$\begingroup\$ @Aganju We do not know how much faster than 10 MB/s the right one is. The left one advertises 90 MB/s. By the class designation they are the same. \$\endgroup\$
    – Crowley
    Commented Feb 23, 2017 at 10:06

On the wikipedia, it says that both a class 10 sdhc card and a uhs 1 sdhc card have minimum writing speed of 10 Mbps.

In this case, the left card has a roman numeral (I) on it. It shows bus speed, and means minimum writing speed of 12.5 Mbps.

I assume that if an sd card on the right can achieve more than 12.5 Mbps, it would have also a roman numeral (I) on it.

So technically the left one is faster.

But it is not just about the speed of the sd card. You have to know how fast can your camera write too.


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