Choosing the right SD card may seem simple enough, but there are actually quite a few factors you should consider to ensure you get the right card for your needs. There are different types and physical sizes available, and each one has its own strengths and weaknesses.
You should look at the maximum capacity and speed class to ensure a card which can hold all of your data and transfer it to and from other devices as quickly as possible. The actual read/write speeds and even wireless functionality are also worth considering before making a final choice and picking a card from a reliable manufacturer.
Types of SD Cards
There are different physical sizes and a couple storage variants to consider as you look at different SD cards, and the right choice ultimately depends your preferences and devices.
SD Card
The original design and still one of the most popular sizes, standard SD cards are commonly found in consumer-targeted digital cameras (professional cameras often use CompactFlash instead). They have excellent speeds and capacities available and are a great choice for general use. While you can use a smaller card in devices designed for SD cards via an adapter, if your device can use an SD card, you should pick an SD card.
MicroSD Card
The next most common design is smaller than the standard model but still offers excellent capacity and speed. This is the size most commonly found in smart phones and similar devices. You should pick a MicroSD card for any device designed to use it, and you can pick up an adapter to make it fit into a computer or reader with a standard SD card slot.
MiniSD Card
This option is very rarely used and its size is just between the standard card and MicroSD. While it offers speeds and capacities comparable to the standard card, there just is not much use for this size due to a lack of devices designed for it. There is simply no reason to choose this card unless you have a device specifically intended for a MiniSD card.
High-Capacity Card
This is a variant that you can typically find as either an SDHC or MicroSDHC card. Standard SD Cards only have up to 2GB of storage, so anything with more than that is a high-capacity model. If you want as much storage as possible on your card, then look for this option rather than a standard card.
Extended-Capacity Card
Here is another storage variant if you need even more space than a SDHC card. You can find this labeled as either SDXC or MicroSDXC and this standard goes beyond 32GB of storage, the limit on HC models. If you need 64GB or more of storage, then XC is the way to go.
Maximum Capacity
In looking at maximum capacity, you have to consider the type of SD card you choose, which has a tremendous impact on storage size. In general, standard SD cards can have up to 2GB of data on them. SDHC cards can store between 4GB and 32GB of data, while SDXC cards have a maximum capacity between 64GB and 128GB of storage, though there is the potential for future XC cards to have up to 2TB of data.
Most cards have their capacity printed directly on them, so simply looking at the card should reveal how much data it can store. Keep in mind that photographs and video take up a lot more storage than text or simple documents, so choose a large capacity option, at least 32GB, for a digital camera or if you like to take pictures with your phone.
Speed Class
The speed class is a simple indication of how quickly data transfers to and from the card. While the specific read and write rates give you more detailed indicators, you can use the speed class to get a good general sense of how fast the SD card transfers data. Classes are indicated numerically, starting at 2, then 4, 8, and finally 10.
Higher numbers indicate faster speeds, but keep in mind that there is also a designation for Ultra High Speed (UHS) starting over at 1. For standard picture taking, a speed class of 4 or 8 should be sufficient, while class 8 is best for video. If you want to capture HD images and video, however, choose an SD card with a speed class of 10 or UHS-1 to ensure the best quality possible.
Read and Write Speeds
While speed class is a good general guideline when choosing an SD card, you should also look at the specific data rates for a better sense of how information will transfer to and from the card. Of the two numbers, read speed is somewhat less important since it refers to how quickly you can access data on the card.
You don’t want to wait forever for your images or documents to transfer from the card to a device or computer, write speed is vital since it indicates how quickly data is written to the card. When using an SD card in a camera, for example, write speed controls how quickly you can snap images and is very important for HD video. Look for a write speed of at least 10MBps to 15MBps, while you want 40MBps to 45MBps for high quality HD pictures and video.
Wireless Functionality
This is very rare in SD cards, but something still worth considering and looking at. Most SD cards work quite simply by inserting them into a device, reader, or card slot on a computer and then accessing the data. There are some cards, however, that include wireless functionality, allowing you to access the data on them through a wireless network or device.
Other factors like speed and storage capacity are definitely more important, but if you have a setup that could really benefit from accessing data on your SD card wirelessly, then look for a model that includes this functionality.
Durability
SD cards are small, plastic storage devices that can include a lot of important data. In order to protect that information, look for models that are designed with durability in mind. You can find cards that have high capacity and fast data speeds and are waterproof, shock resistant, and dust proof. Some cards also include error correction functionality that helps detect any errors and correct them automatically, to protect you from data corruption.
Manufacturer and Warranty
Due to the inexpensive nature of SD cards, there are many different manufacturers out there who make a variety of models to choose from. When looking at different cards, make sure you pick a reliable manufacturer such as Kingston, SanDisk, or Transcend. Other companies like HP, Verbatim, and Lexar also make excellent SD cards. Most of these companies actually offer lifetime warranties on their SD cards, so you know they are built to last, even if they are inexpensive.