The SD card is an integral part of digital life. So many devices we use on a daily basis require them for one purpose or another, but the card that’s right for one device isn’t always right for another.
In this article we’ll take a look at some common, practical uses for SD cards and show you how to make sure you always buy the optimal one for any given activity.
Important SD Card Basics
Before we proceed, you might want to check these mistakes to avoid when buying a microSD card as it clarifies a few facts and common misconceptions. The main points to be aware of include:
- SD vs. MicroSD. These two types of card are identical insofar as they use the same standards, and all microSD cards come with an adapter that enables them to fit into a full SD card slot. However, the write speeds of full-sized cards do tend to be faster than the speeds of their micro-sized counterparts.
- Speed Classes. A card’s speed class –such as Class 6 or U3 — indicates the minimum write speed of a card. This is one important element when identifying cards that are suitable for the task at hand, but it won’t tell you which card is the fastest. You also need to ensure your hardware is compatible with a particular speed class (e.g. UHS-II cards have a different pin layout to older cards).
- Beware of Fakes. You should always buy your SD cards from reputable sellers, and preferably in their original packaging, not a “frustration-free” option. There are lots of fakes on the market.
SD Cards for Photography
If you own a camera, then you will need at least one SD card to store your pictures on. The speed and size that’s best for you depends on the type of camera you’re using. And the speed isn’t just a factor in how fast the camera will save your images, but how quickly it will copy them over to your PC’s hard drive.
For casual photography — using a point-and-shoot camera and shooting in JPEG format — the capacity of the card you choose is more important than the speed. Compact cameras are not known for their fast shot-to-shot time, and with images in the region of 5 MB, your SD card is unlikely to ever be a performance bottleneck.
The biggest consideration is whether you should use a single card with a lot of storage capacity or multiple cards that have smaller capacities each.
If you’re traveling or shooting special occasions, you should definitely consider the latter option. If a card fails when you’re only using one, then all of your images will be gone. If you’re rotating between four cards, you’ll only lose a quarter of your images if one of them happens to fail.
If you’re a more serious photographer who’s shooting with serious equipment — DSLRs, high-end mirrorless cameras, or even an enthusiast-class compact camera — then you should consider both speed and capacity when picking an SD card.
RAW images are much bigger than JPEG images, meaning they’ll typically be somewhere between 20 to 40 MB per image — and can be even bigger depending on your camera. For example, uncompressed RAWs on the Sony A7R II are over 80 MB each.
Factor in the faster shot refresh times, along with burst modes that can rattle off multiple shots per second, and you’re going to be writing a lot of data to your card in a short space of time.
As a result, you should look to get the fastest card your camera supports, which ideally means UHS Speed Class 3 (with U3 printed on the card) or better. The SanDisk Extreme Pro cards are very well regarded for this.
These cards will be large enough to handle the bigger file sizes, too, although you might still want to split your images across at least a couple of different cards to protect against failure.
SD Cards for Videography
All modern consumer video cameras use SD cards, and getting the right one is very important. Use one that is too small and you’ll limit the length of time you can shoot for, and use one that is too slow and you’ll risk dropping frames as the card cannot write the video data fast enough.
The quality of the video you shoot varies based on a combination of several settings, including resolution, bitrate, frame rate, and file format. Using a simple formula, you can use the bitrate to determine what speed of SD card you need.
Bitrate is the amount of data that is written to the card and is normally measured in Megabits per second (Mbps). We know that in computing there are eight bits in a byte, so if you divide the Mbps value by eight, you can convert it into Megabytes per second (MBps). You can then use this value to ensure your chosen card is fast enough.
Action Video Cameras
If you’re using an action camera like the GoPro HERO4 Black at its maximum bitrate of 60 Mbps, that equates to 7.5 MBps using the simple formula above. As long as your SD card is equal to or faster than this, it should be okay.
Class 10 and UHS-I cards have a minimum write speed of 10 MBps, so that’s what you should aim for at the very least. Also, 7.5 Megabytes per second amounts to 27 Gigabytes per hour, so you will be able to record for around 70 minutes on a 32 GB card.
Serious Video Cameras
The above formula applies regardless of the resolution you’re shooting at. However, 4K needs a high bitrate to maintain its quality, while lower resolutions are much more forgiving of lower bitrates. In high-end video cameras, 4K video files will often be much larger than 1080p files.
As a result, there’s a general rule of thumb for buying SD cards for video: at minimum, you need at least Class 6 for 720p, U1 for 1080p, and U3 for 4k.
The main exception to the rule is if you’re buying an SD card to use in a dash cam or any other kind of security camera. Here, length of recording takes precedent over quality, so the bitrates fare often lower.
Again, you should check the speed to ensure you pick a fast enough card, but in most cases you should be able to pick a slower, larger card than a faster, smaller one. Large cards are critical if you want to record and hold a lot of footage.
SD Cards for TVs
Some modern TVs have integrated SD card slots, and nearly all modern TVs have USB ports. By slotting your card into an adapter, you can easily view the photos or video from a camera without needing to copy them to a PC first.
This is dependent on the format you’re using, though. RAW images won’t display, for example, and you’ll need to check your TV’s manual for information on which video formats will play right off an SD card.
SD Cards for Mobile Devices
Many Android smartphones and most Windows Phones have a MicroSD card slot that you can use to augment the built-in storage capacity.
Here, you’ll get the best results from buying the largest, fastest card you can afford while staying compatible with your device. Between the two, capacity is more important than speed for a mobile device.
This is even true of 4K video, which on a smartphone is often heavily compressed. The LG G4, for example, actually uses a bitrate of 30 Mbps for 4K shooting, which is below Class 4 card speeds.
Where you will notice a difference in speed is if you copy files to and from the card regularly (especially large video files) or the first time you drag your massive music collection onto the card. Given the low cost of Class 10 cards now, there’s little reason to choose anything slower.
SD Cards for Data Storage
Most laptops come with a built-in SD card slot these days. It’s primarily designed for getting photos off your camera or moving files from one device to another, but can also be used as an easy way to upgrade your storage.
Secondary Data Drives
If the card sits flush with the laptop’s casing, then you can leave it permanently inserted and basically use it as a secondary data drive.
Unfortunately, on many laptops, the SD card actually protrudes from the slot by several millimeters, creating an untidy look and leaving it prone to being snagged. In these cases, there are a few possible solutions.
Some manufacturers, like the Transcend JetDrive Lite, have SD cards that perfectly fit into MacBook card slots. They may or may not also fit your Windows laptop, depending on the case design. Just be wary of inserting a card that’s too small in case it gets stuck and becomes impossible to remove.
Along similar lines are HyperDrive adapters. Again, these are designed for MacBooks but may also fit Windows laptops. These MicroSD card adapters fit into regular SD card slots but are shorter than SD cards so do not stick out as far. You can find generic versions on Ebay, too, often called MiniDrive adapters.
Either way, if you’re using an SD card for storage, you want the fastest, largest card that will work in your laptop. Preferably 128 GB and U3 speed, with one exception in cases where you use the card to store something like your iTunes library, in which case speed will be less important once you have copied all the files over.
If you can find a card that fits your laptop’s SD slot perfectly, you can leave it inserted as a handy backup drive in conjunction with File History in Windows or Time Machine in OS X.
It’s a better option if you’re doing selective backups, since there are limits to the size of card you can get (e.g. there’s no way to clone a 2 TB drive to an SD card as of now) and the cards start to become less cost effective once you move beyond 128 GB.
The Raspberry Pi needs an SD card (or MicroSD on a Pi2) to install the operating system, but the requirements are modest. You need a card of 4 GB or larger to use the NOOBS app which simplifies the installation and setup process, and the official recommendation is 8GB, Class 6.
You might want to use a larger card so you’ve got space for data storage as well, though you can use a USB flash drive for that if you need to.
Although most SD cards should work on the Pi, some users have experienced compatibility problems with certain card models. Before you settle on a card, it’s worth checking this list of working and non-working cards to see if yours has been tested.
SD Cards for Bootable Drives
A final good use for an SD card is as a bootable drive for your PC or laptop. You can set it up for emergencies if your computer fails to boot or if you want to test drive a new Linux distro.
Many laptops are not able to boot from the internal SD card slot, so you might need to use an adapter and plug it into a USB port. In this case, make sure your adapter is at least USB 3.0 or it will be unusably slow.
To create a Windows 10 boot disk, you only need a card of at least 4 GB, but there’s no good reason to buy a card of this size any more. A 16 GB U1 card is well within most budgets and performs much better.
Which SD Cards Do You Have?
The falling prices of memory cards is making them easier to buy than ever. Unless you have specific requirements, you should never have to settle for a card that’s either too small or too slow.
That said, with a growing number of devices using SD cards, it’s always a good idea to check that you’re getting the right one for the job.
What memory cards do you use? Is there are brand you swear buy, and which ones do you always buy for a specific device? Share your thoughts and recommendations in the comments below.