So you have a camera. It takes a memory card. So which one should you choose? What’s with all this class and MB/s mumbo jumbo? There’s a ton of confusion out there on the subject. Today we’ll look at memory card performance and how it helps us get the most out of our SLRs. An important thing to note is SD cards are the only ones to include both speed and class on the face of the card. Compact Flash and Memory Stick cards only refer to speed, and not class.
SD memory card performance is measured in one of two ways: speed, known as megabytes per second (MB/s), and class (C2, C4, C6, etc.). Understanding the difference of these measurements is often misunderstood, but essential in selecting the card that will best suit your needs.
Speed refers to continuously shooting still images in the burst mode. The speed rating (i.e., 30MB/s) designates the maximum sequential speed that data can be written to the memory card and transferred to a host device. This is also known as “read/write speed.” Lets say you have a card that has a speed of 30MB/s. This means the card will read/write up to but no faster than 30MB/s. The faster the card, the less lag time between frames during continuously shooting in burst mode on cameras that shoot at high frame rates. What’s a high frame rate? Usually a camera that shoots 5 frames per second or higher is considered a high frame rate.
Class refers to recording video. The class rating (i.e., C2, C4, etc.) designates the minimum sustained speed required for recording a constant rate of video onto the card. A card’s class rating corresponds to the minimum guaranteed data transfer rate megabytes per second. This means the card will record video no slower than xMB/s. For example, Class 4 cards are designed for a minimum sustained transfer rate of 4MB/s, while Class 10 cards are designed for a minimum sustained transfer rate of 10MB/s.
Cameras have the ability to record images in bursts up to 10 frames per second. This floods the card with a massive amount of data in an instance. These cameras demand high-performance memory cards with fast maximum write speeds. Current SLRs can produce huge files in either RAW, JPEG, or both. And RAW files can reach upwards of 20mbs. The larger the stream of data being crammed onto a card, the faster the write speed must be in order to handle the load. If a card is too slow, then shooting will pause until the card catches up to the camera, at which point shooting will resume. This lag causes missed shots, which isn’t good. But if a card is fast enough, the camera can shoot non-stop at its fastest frame rate until the card is full. So for fast shooting, a fast card is needed.
If you want to capture high megapixel still images at a fast frame rate? Then you need a card with a maximum write speed fast enough to meet your shooting requirements. Have an entry level SLR (which only shoots around 3-4 frames per second)? Then skip the high-speed cards. But if you have a more advanced camera and intend to shoot faster burst rates (say 5 frames per second and faster), in RAW format, then you will need a fast memory card. Rather than simply choosing the highest performing card in the store, you have to determine what type of shooting you’ll be doing. Then we can select the card that meets your shooting requirements.
Like it or not, we are merging photography and video. Today, most SLRs have the ability to shoot high frame rates and record HD video. And if we are going to be utilizing both, we’ll need memory cards that accommodate both mediums. If the card offers fast maximum write speeds but only a Class 2 rating, then it won’t be fast enough to record in HD. Also, if the card has a Class 6 rating but a slow write speed, then it will suffer a lot of lag when shooting in burst mode.
Again, this only applies to SD cards. If you’re shooting higher end SLRs, you only use Compact Flash cards. Then you only have to worry about speed. If you’re shooting sports, then you need fast cards. If you’re shooting portraits, then maybe not. And what about which brand to choose? Well, I use Promaster brand memory cards. The reason I choose them is twofold. 1) they have a lifetime warranty. If one ever fails, it gets replaced. In 3 years of hardcore shooting, I’ve only had one fry on me. Pretty good in my book. 2) I get a decent price on them at he pro camera shop I work part time at. I know, not nearly as romantic. But it’s a valid reason nonetheless. And to be fair, even if I didn’t work there and get the discount, I’d still choose them because they’ve been so reliable.
So there you go. Class and Speed ‘splained. Hope it helps. Happy shooting everyone
Now, go out and shoot something!
No comments:
Post a Comment