There are so many different SD cards out there. Theres different brands which use different terms, and now there are different types like plain SD, mini SD, micro SD and recently SDHC. It's confusing to figure out what everything means. We're here to help you decide what's best for what you need.
SD stands for Secure Digital. It's just another flash memory card type out there. It's become the standard storage unit for many smaller gadgets such as point-and-shoot cameras, cell phones, and PDAs.
I've had 3 devices which require an SD card of some sort. Some require large amounts of storage and read-write ability. I have a 10 megapixel Digital SLR, 5 megapixel Point and shoot, and an R4 for my Nintendo DS Lite. I currently have 2 2GB cards for my DSLR, and I'm looking for a 4-8GB SDHC so I can take more pictures, and write faster! I've done some research, and I'd like to share the information with you.
First, let's start off with plain old Secure Digital cards. These cards range from about 16MB all the way to 2GB. Of course, there are many brands out there, Sandisk being the most popular (and most expensive), Kingston, OCZ, PNY, and Transcend to name a few.
Most companies go by the same rating system, where they use the "x" (times), but who knows what that really means? On the other hand, Sandisk uses a Standard, Ultra II, Extreme III, and even Extreme IV (for Compact Flash) for their ratings. However, I want to know what this actually means in terms I understand - MB/s.
Sandisk is different from the pack, here are their types and numbers, gathered from their website and benchmarks.
Standard - ???
Ultra II - minimum 10MB/s sequential read; 9MB/s sequential write
Extreme III - minimum 20MB/s read/write
Kingston is also a little different from the pack, but at least they include the "x" rating scheme as well.
Standard - ???
Elite Pro - 50x -up to 8.2MB/s read; 7.7MB/s write
Ultimate - 120x - up to 21MB/s read; 18MB/s write
The other brands basically use the same notation and the ratings are fairly similar.
60x - 9MB/s (OCZ)
80x - ??? (PNY)
133x - 21MB/s (OCZ)
150x - 22.5MB/s (OCZ)
Apart from standard sized SD Cards, they also made variants called mini SD and micro SD. Now, different devices require different sizes. There aren't many devices that use mini SD now, and lots use micro SD, because it really is very small. Most of these memory cards come with adapters to increase its physical size. For example, the Kingston micro SD card I have comes with a regular-SD sized adapter so it will fit in regular SD units. Many micro SD cards now come with a mini SD adapter also. The notation is the same for these cards, when it comes to speed, but they'll be a little bit more expensive than the standard sizes.
Now, for the new technology. SDHC stands for Secure Digital High Capacity. These typically range from 4GB to 8GB, but I've seen some out there that are 16GB, and SDHC has a theoretical capacity of 32GB. Imagine that, 32GB on such a small card. Unfortunately not all SD devices work with SDHC cards, so you have to make sure that your device will before purchasing one of these. Older multi-card readers will not work either. Luckily, many SDHC cards come with a SDHC reader.
With the development of SDHC, they've also created a new rating system that goes by classes. Currently, there is Class 2, 4 and 6.
Of course Sandisk uses different notation again with their Standard, Ultra, and Extreme.
Standard - Equivalent to Class 2 - 2MB/s
Ultra II - 10MB/s read; 9MB/s write
Extreme III - 20MB/s read and write
All other manufactuers use the Class system.
Class 2 - 2MB/s
Class 4 - 4MB/s
Class 6 - 6MB/s
As you can see for some reason, Sandisk has much higher numbers. I'm not sure how accurate they are, but I would really like to test the speed. Especially their Extreme III SDHC card.
Well there are the numbers and now it's up to you to pick the right card for you. Of course the more storage you have then the more data and pictures you can store. The speed may not matter, but it just depends on your device. Cellphones can get away with the standard speed. However cameras, especially Digital SLRs require faster and bigger cards - many photographers shoot in both RAW and JPEG in burst fire. Thats about 12MB in data. Some digital SLRs can also shoot 10 frames per second. So before deciding, know what you are going to use the card for, and get something that fits your needs, and make sure it's compatible. You may end up getting multiple SD Cards like I have.
Note that many manufacturers have a limited life time warranty. Many also have a disclaimer stating 2GB SD Cards may not work in some devices.
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