So, if you’ve used a camera in the last, oh, five or so years, I’m sure you’ve dealt with the joy of memory cards. I’m here today to help you understand the fairly cryptic and confusing ways popular cards, such as Sandisk cards like the Ultra II pictured to the left, tell you how fast they are. This time around we’ll look at SD memory cards (this also applies to SDHC, which is just the High Capacity version of SD).

So, let’s take a look to our left again. See the 15 mb/s printed on the label. It’s really nice when manufacturers give us this, this tells us the fastest the card can write information. If you see the little partial circle with a number in it, in this case “4″, this indicates the SD card’s “class.” The Class tells us the absolute slowest the card will ever write our data, and it’s a pretty easy system. Class 2 SD memory cards will write no slower than 2 MB per second. Class 4′s no slower than 4 MB per second, and of course Class 6 no slower than 6 MB per second.

Now, there’s one other way people will tell you the speed of their cards, and that’s X speed. I’m sure you’ve all seen cards marked like “60x”, “100x”, or “133x” (this system is used for compact flash, as well). In this case one “x” means “1.5 KB per second maximum write speed.” These days, KB are yesterday’s news and we’re on to MBs, so this isn’t the most useful number ever. If you’re confused by x-speeds, just take it times .15 to get the MB per second, which is way more useful. 100x = 15 MB/s, 133x = 20 MB/s, etc.