As far as format wars go concerning digital cameras, SD was the winner. There were a few others in the mix for a while (like the ill-fated xD format), but now just about any digital camera you’d buy will use SD as its primary storage.
The problem afterward is deciding which SD speed class rating to go with. Fortunately it’s fairly easy to figure out once you know your numbers and also know what you intend to do with your digital camera.
General rule of thumb: Photos can use any speed class rating, video needs higher speed class rating.
A digital camera doesn’t care what your SD card’s speed class rating is concerning photos. Even in a brand new camera, you could pop in a class 2 and photos would be stored just fine. The only time you’d notice the slowness is in two situations.
The first is when you take photos at the camera’s maximum possible picture quality, where you will notice a 1 to 3 second pause as the camera writes data to the card after the photo is shot.
The second is when the card has more than 75% of its space taken up with photos. Photo-taking will remain the same speed, but reviewing the photos will take longer because the camera has to index more stuff.
With video on the other hand, that’s a different story.
240p (320×240) and 360p (640×480) video can used with a class 2 with no problem at all, but anything above that requires a minimum class 4.
Most digital cameras today come with the ability to shoot 720p (1280×720) video. Unfortunately, a digital camera will not warn you if the SD card you’re using isn’t fast enough. If you use a class 2 and shoot 720p video with a digital camera, there will be dropped frames, stuttering, audio dropouts and so on because the card simply isn’t fast enough.
When you go above 720p into the 1080p realm (if the camera is capable of that), sometimes class 4 isn’t even good enough and you need a class 10.
Here is a quick rundown of SD class ratings and what they’re suitable for:
Class 2: Photos, 240p/360p video
Class 4: Photos, 240p/360p/720p video
Class 6: Photos, 240p/360p/720p video
Class 10: Photos, 240p/360p/720p/1080p video
What about UHS?
UHS is an SD classified standard and currently there are two versions available, UHS Class 1 and UHS Class 2. Class 1′s are more available than 2 and start at around $20. Class 2′s start at around $40.
Most digital cameras don’t support the higher UHS speeds. For example, the rather expensive Canon EOS Rebel T3i is compliant with UHS-I, but it does not not take advantage of the increased UHS bus speeds. So sure, it’s compliant, but the camera isn’t "smart enough" to specifically instruct the UHS card to drop its voltage so you can get the full 4-bit mode 50 MB/s speeds you bought the card for in the first place.
In other words, on the Rebel, UHS currently is no better than having a non-UHS class 10. And for most other high-end digital cameras, the same is true.
Eventually at some point the UHS class will gain enough market share where you can actually take full advantage of them in digital cameras across the board.
The UHS class that will make everyone go ga-ga in the digital camera world is UHS-II, with a theoretical maximum speed of 312 MB/s. With that kind of speed, you can shoot in 20+ megapixel RAW all day and it’ll be just as fast as compressed mode. Heck, even if UHS-II is only able to achieve half that speed, that’s still an amazing improvement.
If you’re the type that puts a lot of cash into cameras and were wondering when you should make the next big purchase, wait for full UHS-II support in digital cameras at reasonable prices. When available, you can finally switch to shooting in RAW full time and you’ll love it. No pausing, no waiting, and full uncompressed photo quality (although if transferring that data over USB 2.0, that’ll take forever, so make sure you have the appropriate card reader in your PC).
On a final note, the no-brainer purchase right now is SD class 10. It handles photos and video all the way up to 1080p with no problem at all, and it’s widely available and cheap.
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