Clarification on Sandisk Ultra series for SD Cards

[mynameisjizeng]

Hi all,

I'm quite confused.

Most SD Cards use the class system to show their speeds i.e. Class 4 is 4mb/s, Class 6 is 6mb/s.

However, Sandisk Ultra II has the Class 4 logo, but also has "15mb/s" on their cards.

Does this mean that the Sandisk Ultra series generally have faster read/write speeds?


Thanks in advance!

 

[kkcharles82]

Class 2, 4 or 6 refers to the minimum transfer rate that is guaranteed by the SD card consortium. For example, if a card that is 4GB, conforming to SD 2.0 format, it MUST have at least a Class 2 and above rating, if not it will not be granted the compatibility seal.

Sandisk is quoting the tested (their in house testing) SEQUENTIAL write or read timing. Since it is sequential, it is much much faster. The SD card consortium tests the card using RANDOM read and write. In cameras, we only do sequential write or read, so there is essentially no problem. But if you are running a program off SD card in your computer, then it is random read and write. Hope that clears your doubts.

 

[adept1]

You can find real speed tests of various cards at http://www.robgalbraith.com.

 

[mynameisjizeng]

thanks alot!

what exactly do you mean by SEQUENTIAL?

does it mean that Sandisk cards are tested to be faster, or is it just different ways of testing?

 

[mynameisjizeng]

any more help?

 

[mynameisjizeng]

no more help?