By Robert Dubbin and Lori Grunin
August 30, 2005; updated December 16, 2005
What's in a name? Apparently very little when it comes to digital camera memory. It would be great if flash-memory manufacturers chose names such as "CompactFlash fast enough for a 5-megapixel camera but not fast enough for a digital SLR." Alas, for a variety of reasons, we're faced with High Speed
cards that aren't, Extreme
media that's not the most extreme, and Pro
-designated storage that's more suited to a point-and-shoot. Or one manufacturer's fastest card that is slower than another manufacturer's slowest card. With all the noise, how can you possibly figure out which to buy, much less figure out if you're overpaying or if you're getting a bargain?
The bottom line is, no matter how deep you delve into the guts of flash-memory specifications, choosing a card ultimately remains more art than science. Even if we tested them all, there are simply too many variables involved to draw any useful conclusions. (Rob Galbraith
has made a heroic attempt with his CompactFlash Database
, but the only general conclusion we can really draw from his stockpile of data seems to be that we'd rather be herding cats.) Plus, some cameras have hidden limitations; for instance, many models don't support cards larger than 2GB, which requires the use of the FAT32 file system; you'll still need to read the fine print on the camera manufacturer's Web site before you choose a capacity. Also keep in mind that the capacity on the label will always be higher than the actual formatted capacity of the card, just as with hard disks.
So we threw all the info we could amass into a vat, stirred it up, and cooked up some very loose rules of thumb to help simplify your decision. Keep in mind that your camera's read/write speed will affect your overall shooting experience much more significantly than the card you have inside it; a fast card won't make up for a slow camera, and standard-speed memory will bring down only the fastest cameras. But a faster card may also speed the process of uploading photos to your PC and browsing them in the camera.
|If your digital camera resolution is ||We recommend this speed |
sustained write speed)
|And at least this capacity
|4 megapixels or less ||Speed doesn't matter ||128MB |
|5 megapixels ||32X to 50X ||256MB |
|6 megapixels ||40X to 60X ||256MB |
|7 megapixels ||50X to 80X ||512MB |
|8 megapixels ||Fastest possible ||512MB |
|9 megapixels ||Fastest possible ||1GB |
|10 megapixels ||Fastest possible ||4GB |
|More than 10 megapixels ||Fastest possible ||Largest possible |
We're also seeing some manufacturers toss in extras; many bundle software on the card for undeleting accidentally erased photos, which generally costs about $30 when purchased separately. Furthermore, technologies targeting professionals have begun to surface as well. For example, Lexar's LockTight allows security-minded shooters to encrypt the contents of the card in compatible cameras (and read using compatible readers), and its ActiveMemory is a software/hardware solution for streamlining the professional's work flow by populating and passing on the IPTC fields in the EXIF header. Specialty technologies such as these are available only through limited retail channels.