Your digital camera uses a memory card to store your images. Most people look at the capacity of the card but don’t consider much beyond that. But the fact is that there are other factors that affect your photographic experience. So, how do you choose a storage card that is right for you?
The two key features in any card are the storage capacity and the speed of the data transfer. But there are other specifications of which you may need to be aware. The most important thing to remember is that you must read and understand the storage card specifications in your camera’s user manual. In general, you’ll use either a Compact Flash card (CF) or a Secure Digital card (SD).
Compact Flash Cards
Compact flash cards were first developed in 1994 yet with frequent updates it remains a very popular storage option that can be found in many consumer and professional cameras. When compared to SD cards, the compact flash cards are physically larger and more rugged.
The specifications for Compact Flash cards will support sizes from 2MB up to 512GB. On most store shelves, you’ll find Compact flash cards with storage capacities from 32MB to 128GB. Today’s cameras are creating very large image files so cards at the smaller end can be quite impractical.
Transfer speeds in CF Cards can be quite confusing. Originally, the speed was designated by a multiple of the transfer speed of the original CF card which was 15o kBytes per second. So, a card that shows 133X has a transfer speed of 133 × 150 kByte/s = 19,950 kByte/s ≈ 20 MB/s.
Today, you may find transfer rates designated as either a multiple or in actual Megabytes per second. For example, I just bought a 32 GB card with a speed marked as 1066x and 160 MB/s.
When you discuss card speed, you should consider both the write speed, as noted above, and the read speed. The speed at which data from the card can be transferred to your computer. There are many complexities in this area but just know that the current interface, UDMA-7, provides some of the fastest transfer speeds when using a USB 3 connection.
Secure Digital Card
The Secure Digital card is the product of a joint development effort among three major manufacturers. Along with the card specifications, they formed the SD Association, an organization focused on defining the specifications and promoting SD card. Today there are about 1,000 member companies.
The SD Card actually includes three different form factors; the original Secure Digital card, a mini SD card, and the micro SD. All of these formats are much smaller than the Compact Flash cards, making them a popular storage option for compact cameras.
Throughout the life of the SD card, the SD Association has introduced four different families of cards, each subsequent announcement taking advantage of new technology to increase the speed and security of the data on the card. The original card was ironically called the second-generation Secure Digital (SDSC) card. In 2006 the capacity of the card was increased and a new Secure Digital High Capacity (SDHC) format was introduced, supporting capacities up to 32GB. To support the demand for even larger cards, the Secure Digital eXtended Capacity (SDXC) was introduced that supports capacities up to 2TB.
Even within the SDXC family, there are different versions that define throughput speeds. Some of these new specifications require a new row of pins or contacts on the card. This means that not every camera can take advantage of all the new features of these advanced cards.
The other thing that helps with the speed of the SD card is the type of data bus the card supports. There are three different Ultra High Speed (UHS) data buses. When shopping for cards, the bus type is identified by the roman numeral I, II or III.
As you can see, there are a lot of things to think about when buying a storage card. If you have special needs for speed or capacity, it’s best to visit your local camera store to find out what is the best card for your needs.