What Does an SDHC Memory Card Class Mean?

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SDHC memory cards make it possible to easily save large amounts of data when you're doing video recording or digital photography. But if you want to get the most out of your digital video or image processing, SDHC memory card classes are important to consider. Proper pairings of memory card classes and devices will maximise your performance.


SDHC Memory Card Classes are speed classifications for SD memory cards. While all SD memory cards are compatible with SD-based devices, pairing the proper card with the right device will allow you to maximise data transfer speeds. The exact transfer speeds can vary, but card classes allow for data transfer times to be standardised. Card classes include most types of SD cards, ranging from SD to microSD cards.

Class 2

Class 2 cards utilise the normal speed bus and are categorised in the standard Speed Class. Class 2 is the slowest of the four card class groups, so it's best used for recording SD video. Class 2 cards typically have a data transfer rate of around 2 MB per second.

Class 4 and 6

Class 4 and 6 cards also take advantage of the same speed bus and categorisation. Their improved data transfer speeds make them better for some HD recording--Class 4 and 6 cards have transfer speeds of 4 MB and 6 MB per second, respectively.

Class 10

Class 10 cards are the second-fastest group of cards. Unlike Class 2, 4 and 6 cards, Class 10 utilises a different speed bus, which helps it process data much faster. Class 10 cards have data transfer speeds of up to 10 MB per second, which makes them suitable for full HD recording and consecutive HD video.

UHS Speed Class 1

UHS Speed Class 1 cards utilise a proprietary speed bus and card format--UHS-I cards differ from standard SDHC cards. However, this gives the card format vastly improved performance. SanDisk's UHS Speed Class 1 cards have data transfer speeds of 10 MB to 45 MB per second.

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