Wednesday, December 19, 2012

How To Choose The Right SD Card For The Job


Sent to you by Chris Hunter via Google Reader:


via MakeUseOf by Joshua Lockhart on 12/19/12

SD cards are the most common form of removable data storage for portable devices that we have to date. However, many people have had situations where they put the card in their device, and it does not read. Other times, it fails to record. Often, it always ends with the person saying, "Well, I thought I had enough storage!"

But that's just it – SD cards aren't all about storage! In fact, there are several other factors to consider, and when purchasing your cards, you should make yourself aware of them. That said, SD cards aren't all created equal, and it's important to be educated as to what separates each one from the rest.

As a given, all types of data are different, and although I can't tell you exactly what to buy since I don't know your device, I can supply you with the proper information to make that decision on your own.

The Elements

When purchasing a SD card, you should take into consideration four main factors. Granted, your manual (you know, that thing you tossed in the trash as soon as you unboxed your device) may actually have recommendations as to what kind of card you should get. Even still, it's good to know about them:

  • Class
  • "X" Rating
  • Storage
  • Size

There are four different SD card classes that you can buy. You can grab a Class 2, a Class 4, a Class 6, or a Class 10. This class number simply lets you know the minimum write speed of the card. But what is that number? Well, that's easy. The number of the card denotes the minimum MB/s that the card can write. For instance, a Class 2 writes at 2 MB/s. Furthermore, there are even ultra-high speed (UHS) cards which can transfer anywhere between 50 MB/s to even 312 MB/s and up.

The "x" rating (or x speed) is actually just how many times faster the card writes down information compared to a standard CD-ROM drive. As a note, these drives write data at about 150kB/s (or 1.23Mb/s). For your information, a Class 2 card has an "x" rating of 13x. Why? Well, I prefer to do this math with megabits, but we can see that 13 times 1.23Mb equals 15.99Mb. Since 8 megabits equals a megabyte, divide the 15.99 by 8, and we get about 2MB. Thus, this is a Class 2 with a 13x rating. (I hope that made sense.)

As a note, some cards will blatantly display the "x" rating and some won't. Ultimately, you just need to focus on the MB/s. Classes and "x" ratings are just easier ways of explaining it.

As far as storage goes, this is just based on the type of media you are wanting to hold. What I would suggest is checking out the average size of each bit of media you are recording (everything is different), and then you'll be able to determine roughly what you need. However, there are currently three primary types of cards with different capacities:

  • SD – Not used as often; can hold up to 2GB
  • SDHC – The upgrade to the original SD (a.k.a. SD 2.0); can hold up to 32GB
  • SDXC – The upgrade to the SDXC; can hold up to 2TB


Moving right along, there are actually three different sizes of SD cards that you can choose from:

  • Standard size (32mm x 24mm)
  • Mini size (31.5mm x 20mm)
  • Micro size (11mm x 15mm)

Each of these pertain to the device, and you should be able to tell anyway. Smartphones may use smaller SD cards than cameras, but they are still SD cards, nonetheless.


Which Card Is Right For You?

For photos, I would recommend focusing primarily on the storage (but not just that). If you're shooting snapshots with your Nikon Coolpix, you could get away with something in the zone of 4 to 8 gigs. However, when it comes to hi-res RAW images, you have little more to worry about. Let's take a slightly closer look at card specs for your devices.

Let's hypothetically say an average RAW image for my camera is about 25MB. Well, considering there are about 1000 megabytes in a gigabyte, that would mean my 16 gigabyte card can hold about 650 RAW images. Of course, this could always vary. Do the same math with your point-and-shoots, and this should help. As for speed, pay attention to the recommended Class Rating and "x" rating.

For video, the SD Association (yeah, that exists) actually has a few recommendations. Here they are:

  • Class 2 – SD Recording
  • Class 4, 6 – Full HD Recording
  • Class 10 – Full HD Recording and HD Still Consecutive Recording

In theory, this should work. However, once again, these are just the minimum requirements. If the camera actually requires a higher "x" rating, then you would be better off purchasing a higher quality card. For instance, if you put a 40x card in a device that requires 50x, the card won't be able to function properly.

For smartphones and tablets, you'll find yourself looking at the same information. You simply need to know the rate which data is written to the card, and you also should know about how much data you need to store.

All in all, I'd say data usage varies quite a bit, and it's hard to pinpoint every single device. Now that you know what to look for in a card, you can apply this information to your own toys.

Which Card Will You Buy?

This is a good rundown of what to look for in your next SD card purchase. Much like when looking to purchase a car, it's good to know what exactly that each bit of data means so you can make an educated decision. Ultimately, you should be able to get a feel for what's good for you.

For more articles about memory card and selection, you should check these out:

What kind of card will you buy? What devices do you have that utilize SD memory cards?

Image Credit: JusbenWikipedia

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