SD Card 101: Understanding the Types, Formats and Sizes for Storing Media

An SD – “Security Digital” – Card is a memory card which stores most of the important data contained on your portable devices, like smartphones, tablets, and cameras. There are many types, formats and sizes of SDs for different devices, so here is a guide to understanding which is right for you.

Different Types and Formats

SD cards often come with decent warranties and can even be water, shock, magnet and x-ray proof! Nevertheless, they are fairly fragile and should be handled with care. SD cards are sorted firstly by their ‘family’, which indicates their data storage and other capabilities. There’s SDSC (Standard Capacity), SDHC (High Capacity), SDXC (eXtended Capacity), and SDIO (combined input/output functions and data storage). SDSCs offer up to 2 GBs of storage space, SDHCs offer up to 32 GBs and the SDXCs go up to a whopping 2 terabytes (i.e. 2000 GBs). SDIOs come in a variety of sizes but their main feature is expanding the range of input, output and memory functions available, such as internet service and GPS.

Different Sizes and Speeds

There are also three sizes: standard (1.26×0.94×0.083-0.055 in), mini (0.85×0.79×0.055 in) and micro (0.59×0.43×0.039 in). Adapters are also produced to provide compatibility between smaller SD cards and machines with larger slots, allowing for some backward compatibility with older devices. There are still, however, issues with compatibility across families, sizes, devices and operating systems. While SDSC and SDHC cards are available in all sizes, SDXCs are not available in the mini size and SDIOs are not available in the micro size.

An SD card’s speed refers to how fast it’s able to write and read information to and from the card. This is especially important for video quality as slower speeds lead to lower quality footage. The age of the SD card, the occurrence of file fragmentation and lagging are all signs of poor speed. SD Card Speed Class ratings range from 2-10 MB/s, although higher ratings go up by ‘times’: 80X (12 MB/s) to 300x (45 MB/s) and UHS-I (up to 50 MB/S) to UHS-II (up to 312MB-sec). The SD Association defines appropriate uses for SD Cards by their Speed Classes. Class 2 is said to be suitable for standard definition video, Classes 4-10 are better for high-definition to full HD recording and UHS Speed Grade 1 is recommended for real-time video broadcasts. SDHC and SDXC generally offer the highest speeds. Make sure your device supports the speed rating of your card, and look for greater range on large online stores like rs-online.com if you’re struggling to find the right fit.

Protection and Formatting

SD cards offer two layers of protection. They can be locked by their host devices with a password, which then requires sign-in to write or read information. Many SD cards also include DRM copy protection. It’s possible to reformat your SD card on a compatible computer or phone, though the procedure for doing this varies slightly between devices and operating systems. When reformatting on a computer, make sure you’re logged in with admin rights, insert the SD card into your computer’s SD card reader, navigate to the SD card under “Devices with Removable Storage” or a similar menu label, right-click and select the “format” option and follow prompts. On a mobile device, insert the SD card into your mobile’s slot, navigate to “settings” then to “memory” and “format”.

Consider writing up a list of questions to ask your retailer: given what you now know, what detail of answer would suffice? Check out the SD Association FAQ for further questions.

Isabel Ward is a photographer who also dabbles in graphic design. Her files on her computer are like gold to her so backing up is something she has to be vigilant about.

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My name is Gary, a 31 year old Tech Loving marketer passionate about home tech and coffee.

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