Virtually all digital recording devices, be it a mobile, camcorder, camera and many others, require the addition of a memory card in order to store your data (unless it’s an Apple product naturally). Not all of them though come with these included, or if they do, they can be very low capacity versions.
The most common solution in digital cameras is the flash memory card known as an SD or SDHC card. There are 3 different sizes to the SD card, but most devices take the standard, and largest size which are about 3cm x 2cm in size and have the top right hand corner cut off. This is the size I’m going to focus on.
Buying a flash memory card for your camera can be pretty confusing, there are loads out there which vary massively in price. I’m not going to go into massive detail about the differences (but here’s a blog that does if you’re interested) but thought it would be good to explain a couple of the variations to help people decide which one to buy.
Firstly, what’s the difference between SD and SDHC? You see both there stamped on cards, and your instructions should make it clear which version you need, but in essence there is only one thing you need to know. SD was the original format (stands for Secure Digital) which was invented by a company called SanDisk. SDHC stands for Secure Digital High Capacity and is a more recent invention. SD cards stop at 2GB and are slower at writing the data than SDHC cards. Not all devices can take SDHC cards, so do check, but most of the products you could buy at the moment now use this SDHC format. Visually there is no difference between SD and SDHC cards other than those letters being printed on the card so pay attention to this when buying.
The second thing to compare is the total capacity of the card. This can vary massively, but in modern times I wouldn’t consider anything below 2GB or even 4GB as the minimum for a digital camera. The more memory the card has, the more images or video you can store on it, but the more you’ll pay. You can get up to 32GB or even 62GB pretty cheaply now, but I know some photographers recommend using more, lower capacity cards, so you aren’t totally reliant on one that might break. I tend to go in a happy medium of 16GB for my DSLR (the images from which are big in memory size because I shoot in RAW format) and find 4GB more than enough for my compact digital camera (where I shoot in the standard JPEG format).
The final aspect to mention, and the least well known, is the speed rating of your card. Whilst SDHC are quicker than SD, you do need to understand that not all SDHC cards write the data, or display/ transfer the data a the same rate. In order to help, SDHC cards have a speed rating printed on them too. These are displayed as a number inside a letter C shape (see images below). In simple terms, the higher the number, the quicker the card. The rating starts at 2 and goes up to 10, with the most common being 4, 6 and 10. The minimum to look at these days is a speed rating of 4 (entry level speed for HD video requirements) which write at around 15 megabytes per second (MPS).
If you do a lot of burst shooting with your camera (lots of shots at once) then you should look to go up in speed or the card may struggle to keep up with the number of shots you are taking. Class 6 write at 20 MPS with class 10 going up to 30 MPS. Some SDHC Class 10 cards even claim they can write at up to 45 MPS. If you do a lot of HD filming or want to take lots of high resolution stills very quickly then Class 10 is what you want. As to be expected, the higher the speed rating, the more you’ll pay. Prices have tumbled on these in recent times though so I now always plump for the Class 10 cards to be safe. I find that Class 6 is usually 50% more than Class 4 and Class 10 is double the price of Class 4. I use a class 10 in my DSLR (I do a lot of burst shooting) but find class 4 more than enough in my compact as I don’t take much video with it.
Here are 3 visual examples from SanDisk which clearly show the 3 variable elements to look for which are the same on all cards.
1) SDHC card, 8GB capacity, speed rating of class 4
2) SDHC card, 8GB capacity, Speed rating of class 6
3) SDHC card, 16GB capacity, speed rating of class 10
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Hi, great blog about SD cards. Only point I would add is aimed particularly at people using SD cards in active situations. A lot of the more expensive cards will be less likely to fail through physical damage, abuse or water ingress. For example the top end SD cards from Panasonic, who co-created the format with Toshiba & Sandisk, can withstand immersion in water up to 1m deep for 30 minutes and are resistant to quite severe bending & twisting (think jeans pockets!). They also have integrated safety systems to prevent loss of data due to power failure or incorrect removal of cards from devices. (http://goo.gl/SuuYO) I’m sure that other higher end brands have similar features so it’s worth looking into if you’re likely to get wet or are particularly accident prone!
A fair point, well made. I think the decision to buy more expensive, consumer branded versions of any product applies in many situations from cards to HDMi cables etc. I think these comparisons are more easy to understand than the speed and class ratings on cards. The added benefits to the top end cards should be read and understood though before making the buying decision.