This table clarifies the speed equivalencies of the different speed classes, and what video you can record with it. With three different speed classes (plus A1 and A2), things can get a bit confusing. In other words, C6 and V6 are the same speed but only V6 will definitely record 1080P video. They use a ‘V’ symbol followed by the same MB/s number seen in the original Speed Class. From UHS-II and onward MicroSD cards have 16 pins – an extra row – to achieve the new speeds.ĭefines a set of minimum requirements for memory cards for recording progressive-scan video. In the original SD Card is was 12.5 MB/S but this has increased with UHS-I, UHS-II and UHS-III. Ultra High Speed: This is the speed of the bus which transfers data to the host device. The next generation specification, settled in June 2018, supports cards up to 128 TiB (1 Tebibyte is 1024 GB), however it is still not in regular use yet. Announced in 2009 this was version 3 of the SD specification, adopting exFAT file system and extending the theoretical storage limit to 2TB. This was the first step up in card size, from 2 to 32GB max, but used the same pins. Secure Digital High Capacity, otherwise known as Secure Digital version 2, arrived in 2006. It’s usually quicker to read information off a card than to put it on, so look carefully at the quoted speeds. That means a data transferred at 10 Megabits per second would take eight times as long as 10 MegaBytes per second. Thoroughly deleting the device (formatting and starting again) or using a defragmentation tool is a good solution.Ī byte is 8 bits, and a bit is the smallest unit of information storage on a microSD card. Over time adding and removing files can leave a number of fragments of files which will slow down accessing the card because the device needs to move between each fragment as it reads or writes. When a microSD card (or any disk system) stores a file, it might need to split it into pieces to fit around information already on the card. Since SDXC and their MicroSD equivalent cards came along, they’ve required use of the newer exFAT system, so it’s a good idea to be sure you use it too if you’re reading cards on computers. These are file systems – the FAT stands for File Allocation Table – and exFAT is the newer format for saving files (that’s not to say you aren’t old enough to remember FAT16, but it’s no use on newer SD cards). IOPS is used because it’s a useful way of measuring the speed of the kind of computing operations that applications undertake, as opposed to simply reading or writing a large file.Ĭlass 2 (A2) Application Performance Class also called SD Physical 6.0 spec, with a write speed of 10Mbytes/sec and minimum random read of 4000 IOPS (Input/Output Operations Per Second) and random write of 2000 IOPS. MicroSD GlossaryĬlass 1 (A1) Application Performance Class also called SD Physical 5.1 spec, with a write speed of 10Mbytes/sec and minimum random read of 1500 IOPS (Input/Output Operations Per Second) and random write of 500 IOPS. For more, see our primer on how we test and review on Digital Camera World. We use our findings to inform our comments in reviews and buying guides. With storage devices like microSD cards, we look at the compatibility, transfer speed and hardiness of the device, and weigh it up against the asking price to determine if the card represents good value. How we test microSD cardsĪt DCW, we subject all photo and video gear that comes our way to our rigorous testing standards. (Note that the Ultra card is available in larger sizes - but with the SDXC logo which will mean it will be incompatible with these older devices). If you’re trying to help out an older device limited to HC and U1, then the SanDisk Ultra is a good choice – as these may well warn you not to use larger than 32GB cards, due to incompatibility with more the more recent card format. The HC in SDHC stands for High Capacity, and the choice of those words is what left the industry needing XC soon after.
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