SD Cards, also known as Secure Digital memory cards, are one of the most ubiquitous type of memory card used by digital cameras today. They’re used by everything from compact digital cameras to professional mirrorless cameras, and even mid-range digital SLRs.
SD (Secure Digital) cards come in a huge range of sizes and speeds, so how do you know which card to get? If you’re shooting 4K video, read our guide to choosing the best 4K video memory card.
If you’re shooting photos, the type of card you choose will depend on the type of camera you use, how much you shoot, and what you’re shooting.
There are three main factors to consider with SD cards:
The size in GigaBytes (written as GB) – this is important because it determines how many images you can store before having to change your card. It’s generally considered good practice to have multiple cards of a smaller size, rather than one large card as it spreads the risk. If one card is corrupted you’ll only have lost some of your images, not all of them.
The write speed - written as MB/s which means MegaBytes per second and describes how quickly your images will be saved to the card (not to be confused with MegaBITS per second, which is how video quality is described – 1 byte = 8 bits). This is important because it affects how quickly you can shoot and how many images you can shoot in sequence.
The Class of card – there are two of these! Firstly the ‘Speed Class’ which is written as a large C with a number inside, and secondly the ‘UHS Speed Class’ which is written as a large U with a number inside. These classes indicate the minimum writing speed of the card. They are more relevant to video recording than stills photography, and some cameras will require a card with a minimum UHS or Speed Class.