SD Cards

Mobile devices, such as cameras and tablet computers, use SD cards for transferable memory that holds data, applications, pictures, audio files and video footage. They come in standard SD and microSD™ varieties, with microSD as the standard for small, portable electronics, such as cameras, and SD common for tablets and professional video equipment. These cards vary in some important features, and which one to buy largely depends on what users need them for.

SD Cards' Storage Capacity
Storage capacity is the first consideration when choosing an SD card. The lowest-rated (and most affordable) cards offer around 1GB of storage space, which is all that a typical tourist or occasional photographer usually needs. Users can even use low-capacity cards for some video projects, provided people frequently copy over the content to hard drives to free up space.

Larger SD memory cards can hold application data or large files for transfer between computers. They're also good for shooting video and to have on hand during long trips when copying data is not convenient. The technology of a card limits it to about 2TB of storage space, which is almost always more than enough.

SD Cards' Read/Write Speeds
Another factor affecting the performance of a memory card is the speed at which it transfers data, usually expressed as its read/write speed. A card's writing speed is often very important. The faster data writes over from the camera to the card, the sooner the camera is ready to take more pictures. For casual shutterbugs, this isn't usually a big deal, but for professional photographers, it can be very important. The class denotes its write speed. Thus, a Class 2 memory card writes at 2MB per second, while a Class 4 writes at 4MB per second. A UHS Class card is much faster. A UHS-II card theoretically writes at up to 312MB per second, which is very helpful for high-speed photography and HD video.

The reading speed is much less important for its overall performance. Being able to quickly write data to a hard drive saves a few minutes when it's time to upload and edit pictures, but for most cards, there isn't a significant difference here.

SD Cards in Extreme Environments
Because memory cards find uses in so many mobile devices, especially in cameras, it's inevitable that some end up in harm's way. Hikers and emergency workers, for example, may want to invest in cards that are waterproof, shockproof, and resistant to temperature extremes. Security workers and people who work in labs may need x-ray protection or cartridges with special shielding against strong magnetic fields.

Do SD Cards Have More Capacity Than MicroSD Cards?
Some full-sized SD cartridges have greater total storage than the smaller microSD cards, but this is only relevant on the very high-performance end of the market. Most microSD cards have the same features and storage capacity as their equivalently priced full-sized counterparts.

Can MicroSD Cards Work in Slots for SD Cards?
MicroSD cards started as a smaller alternative to full-sized SD units, but the two technologies are complementary. Rather than creating two standards to work with, the industry offers small and affordable adapters that allow microSD cards to work in SD slots.