Tech Tuesdays: Memory Card Class

The price tags on many memory cards have recently begun to drop. These days, a 4GB SD Card can be picked up in your local drug store for a fraction of the cost for the same card sold only a couple of years ago.

With inexpensive memory cards flooding the market, photo buffs may inadvertently overlook one of the most important traits in a memory card; it's class.

Most memory cards that can be picked up in your local Staples, CVS, or Best Buy are Class 4 or Class 6 memory cards. These cards are perfect for your standard point and shoot cameras like the Canon Powershot or a Kodak Easy Share camera.

What if you're using your Canon Rebel T2i to shoot video? If you use a Class 4 or a Class 6 memory card, you're going to get some funky video if you attempt to pan, zoom, tilt, or are not one of the 0.01% of the population whose hands never shake when holding a video camera.

In the following clip taken on my honeymoon in St. Lucia, notice what happens when the camera is moved quickly (Roughly 20 seconds in). The camera being used is a Canon Rebel T2i with a Class 4 SanDisk 16 GB SD Card. If you watch the video all the way through, my wife decides to enhance the video with a little bit of post marital excitement induced dancing.



If you rewind at the point where the camera shifts, check out the top right hand portion of the video, in the blue sky area. Notice the artifacts that appear (wavy lines). The slow memory card is attempting to catch up with all the information the camera is trying to send it. A slower write speed doesn't allow for the information to be properly processed, therefor the artifacts begin to appear in times of "high information overload".

To combat this problem, use a Class 10 memory card. With write speeds up to 30 MB per second, a 16 GB Class 10 SDHC Memory Card made by SanDisk will cost you roughly $100 while the 32 GB version with the same speed will cost you closer to $200 per card.

Check out this footage that was shot with a Panasonic HMC150 Camera, using a 32 GB Class 10 SDHC Memory Card. Notice that despite all the zooming, moving, panning, and general hand held insanity, the video looks crisp, clean, and artifact free.