购物时间:教你如何选购SD卡

ROBERT SIEGEL, host: Here's a modern-day version of batteries not included. If you're buying a digital camera or other electronic gadget this holiday season, there is one more thing you'll likely have to throw into the shopping bag. It's not batteries. They are included typically, but an SD card isn't. That's what lets you store all those family pictures, videos and hit ringtones（铃声）.

But choosing the right SD card can be as overwhelming as buying the gadget itself. Dan Ackerman, a senior editor at CNET.com is here to help. Welcome to the program, Dan.

Mr. DAN ACKERMAN (Senior Editor, CNET.com): Good to be here.

SIEGEL: And SD cards come in different sizes?

Mr. ACKERMAN: Well, SD cards come in one size physically and they should fit all the types of devices that take SD cards. But there are different sizes in terms of the capacity of the card. And of course, there are different speeds of the card, so it can get kind of confusing.

SIEGEL: Well, typically what kind of speeds are there?

Mr. ACKERMAN: Well, they call speeds classes（速度等级） when it comes to SD cards. And what they're really measuring is how fast data can be written to the card. Now, if you're using a digital camera, that means when you take the picture, how fast does the picture get written to the card so then you're ready to take another picture? And you've ever taken a photo with a digital camera and had to wait a few seconds, then you know what I'm talking about.

SIEGEL: But that's different from size of the ….

Mr. ACKERMAN: And the size, of course, is 4 gigs(=4G), 8 gigs, 16 gigs. That's how many pictures or how much video you can put on a card. And, of course, you can put other things on cards, too. If you use them in, let's say, your laptop, they're really almost like portable hard drives.

SIEGEL: But typically, can the same, say, digital camera, take a variety of different sizes and speeds of SD cards or would the gadget be limited to a particular kind of card?

Mr. ACKERMAN: Pretty much most digital cameras will take any SD card you can go to a store and buy. You might want to make sure if you have an older digital camera and you want to buy a newer SD card that's larger than, let's say, 4 gigabytes, that it can take what they call an SDHC card, which is an SD card that just has a higher capacity. That's what the HC means, high capacity.

SIEGEL: And is cost generally proportional to size and speed?

Mr. ACKERMAN: Cost is proportional to size and speed. But the price on these cards have come down so much over the years, you could very easily get a very large, very fast card for, you know, $25.

SIEGEL: SD, by the way, I've learned, stands for secure digital card. How reliably secure are these cards?

Mr. ACKERMAN: They're certainly more reliable than the old platter(圆形磁盘片) spinning hard drives that you have, let's say, in your computer because they have no moving parts inside. So they're very unlikely to fail.

SIEGEL: So if there's somebody who is going to be standing in front of a rack, having bought a new camera, say, and wondering what kind of SD card to purchase for it, is there any single little gem of wisdom you can offer?

Mr. ACKERMAN: I would say, get as big and as fast a card that fits within your budget. You can get a 16 gig class 10 card, I think, for 25 bucks, which certainly sounds reasonable to me. If you're not going to be shooting HD video or doing semi-professional photography at, like, sporting events or weddings, you can trade down a little bit and get a class 6 or class 8 card. But they're so inexpensive, I really wouldn't bother.

SIEGEL: Dan Ackerman, thank you very much for talking with us.

Mr. ACKERMAN: Thank you.

SIEGEL: That's Dan Ackerman, who is senior editor at CNET.com.