Picking the Right SD Card: What Do the Numbers Mean? - 42West (2024)

If you’re doing any sort of work in digital media, there’s a pretty good chance that you’ve found yourself needing to purchase an SD card (or “Secure Digital”) for your device at some point. Everything from drones and smartphones to action cameras and regular cameras use SD cards in one form or another, and while shopping for a card to use may seem trivial, it’s absolutely crucial to purchase the proper card for the task at hand to avoid gear malfunctions, or worse, data loss.

What are the Types of SD Cards?

There are far more varieties of SD cards available than ever before. If you’re in the market for some new memory cards for your digital camera, smartphone, or other handheld devices like the Nintendo Switch, and you’re confused about the different titles, ratings, and sizes, you’ve come to the right place!

As you explore the range of memory cards on the market, you’ll most frequently come across three main configurations: SD memory cards, microSD cards, and compact flash memory cards. Each of those three types features many variations based on read and write speeds, size capacity, and classification.

Slower memory cards, lower class ratings, and small size capacities are sufficient for older models of phones, point-and-shoot digital cameras, and video cameras. However, if you’re using the latest technology with robust data processing capabilities and larger file sizes, you’ll need to select more advanced memory cards to ensure everything works as it should.

1. SD Memory Card

SD stands for Secure Digital and it is the basic name for any of the popular postage stamp-sized data storage cards. Early SD cards could store up to 2GB of data and they quickly became the most popular type of data storage for cameras.

The original version of SD memory cards, featuring the FAT16 filing system, isn’t available anymore because the technology is now obsolete. Colloquially, we still call all cards in the SD family “SD Cards.”

2. SDHC Memory Card

SDHC stands for Secure Digital High Capacity. These cards hit the market in 2006 and vastly increased the capacity potential for SD cards. The technology included in SDHC cards can hold up to 32GB of data, which is more than enough for many simple cameras and smaller devices.

SDHC memory cards are still produced and are extremely inexpensive because they’re the most basic type of SD card on the market. They feature a filing system called FAT32.

3. SDXC Memory Card

SDXC stands for Secure Digital eXtended Capacity. The SDXC memory cards were developed in 2009 and exponentially increased storage capacity once again. They have up to 2TB max capacity and a filing system called exFAT, and many professional photographers prefer SDXC cards for their fast speeds and convenience.

Instead of needing to swap out memory cards after every couple hundred exposures, photographers can shoot upwards of several thousand images depending on the file sizes their cameras produce.

4. MicroSD Memory Card

You’ll find microSD in smaller, low-power devices such as smartphones, tablets, or portable action cameras like the GoPro. The microSD card is roughly the size of your pinkie nail, available in a variety of speeds, and comes in capacities up to 2GB. Generally, microSD cards also include a microSD-to-SD adapter so you can use it in a standard SD card reader or device.

5. Micro SDHC

Just like the name of their full size counterparts, the SDHC in Micro SDHC cards stands for Secure Digital High Capacity. These tiny cards can contain between 2GB and 32GB of data.

Many cell phones use Micro SDHC cards to provide consumers with the option to expand their device’s memory. The requirements for cellphone Micro SDHC cards is pretty minimal, so you can often get away with using any basic version regardless of speed or size.

6. Micro SDXC

As storage capacity technology has continued to improve, memory card manufacturers like SanDisk, Kingston, and Lexar took advantage of upgrades to provide even more storage in the MicroSD size.

Micro SDXC refers to Micro Secure Digital eXtreme Capacity. These cards can hold between 32GB and 2TB. Drones, action cameras, 360 or VR cameras, and other extreme-definition devices commonly use MicroSDXC cards for capturing footage.

Manufacturers have begun to replace MicroSDXC cards with even larger capacity Micro Secure Digital Ultra Capacity (SDUC) cards.

7. Compact Flash Card

Compact Flash cards were the most common means of image storage for early digital cameras and DSLRs. SanDisk first developed CF card technology in 1994, and the tech has come a long way since then.

While CF cards are far less common and popular today, many larger DSLR cameras still use them. CF cards tend to be more expensive than their SD card counterparts, but many photographers prefer them because they’re less delicate and easier to handle.

What are the Advantages of Using SD Cards?

There are many reasons why SD cards have come to dominate the storage market for computers, cameras, cellphones, and other small devices. Here are a few of the top benefits of SD cards.

1. Physical Advantages

SD cards are extremely compact and easy to carry and store. Because they feature a universal size and shape, it’s easy to find a range of storage containers for them. Whether you prefer a waterproof, shockproof memory-card case, or a binder with sleeves, SD cards are small enough to carry and store as many as you want at home or on your travels.

You can even use them to replace portable hard drives or flash drives.

2. Solid-State Technology

Another great benefit of SD cards is their solid-state technology. SD cards have no internal moving parts, so they’re less prone to physical failure than other data storage methods. You don’t have to worry about fatiguing joints or connection points.

3. Pricepoint

SD cards are incredibly inexpensive. Whether you invest in very-high capacity cards, or slightly lower capacity cards, you can easily carry plenty of storage with you without spending a ton of money.

As new SD card tech comes out, prices will generally be expensive at first. However, there are so many manufacturers on the market that prices will drop significantly in short order.

SD Storage Capacities and Compatibility

The amount of storage that you need on your SD card varies tremendously depending on which device you’re using it with and what exactly you’re going to be creating with that device. For example, files from an audio recorder are significantly smaller than 4K video files from a video camera. Understanding what kind of files your device is creating is critical to making the right decision on capacity.

If you’re shooting HD video or RAW photos with a DSLR or mirrorless camera, you’re best off with getting the highest capacity card you can afford. HD and 4K video files can be astronomically large, and RAW photos of any modern resolution can be quite big as well. For other uses such as audio recording, smartphone/tablet use, or a consumer-level point-and-shoot camera shooting jpeg images, a smaller SD card will suffice.

SD and Micro SD Card Speed Class Ratings

What do we mean when we talk about speed class ratings? For starters, we’re talking about data read speeds and writing speeds.

As camera technology improves, memory card manufacturers needed a way to demonstrate the speed capabilities of their memory cards. Fortunately, speed classification is standardized so consumers always know what to expect when investing in new memory cards.

The SD Association is the international organization formed to maintain these basic standards for SD cards and Micro SD cards.

Three Main Classifications for SD Cards

There are three primary classifications for all SD Cards regardless of manufacturer. Those classes are Speed Class, UHS Speed Class, and Video Speed Class. We’ll go into greater detail about UHS Speed Class in a moment, as it’s the most common speed class used by photographers. But first, let’s explore the original classification for SD cards.

Speed Class is the original classification and is denoted by a large “C” symbol. Within C Class are C2 (Class 2), C4 (Class 4), C6 (Class 6), and C10 (Class 10). In each of these classes, the minimum write speed is represented by the number in the name. For example, C2 has a minimum write speed of 2MB/s while C10 has a minimum write speed of 10MB/s.

If you still have old C-class cards in your camera bag, you may feel tempted to recycle them in favor of newer, faster memory cards. If you use an older camera or camcorder, however, changing your cards may not be necessary. But if you’re trying to record video at 4K resolution or better, it’s time to upgrade your cards.

The speed of the card you purchase is truly one of the most crucial aspects of buying an SD card and is one that’s often overlooked by those unfamiliar with SD speed class ratings. It may seem complicated at first, but in reality, it’s fairly simple to understand.

U1 vs U3 SD Cards

With so many symbols, numbers, and specifications listed on SD card labels, it can be tough to keep track of what they all mean and how important they are for specific uses. For example, U1 cards were once top of the line, but now U3 cards are more common.

U1 and U3 refer to the write speed of the cards. U1 can write up to 10MB/s while U3 can write up to 30MB/s. That’s a big difference considering the size of most image and video files created by contemporary cameras. Cameras capable of creating very high-resolution images while shooting in high-speed burst mode and shooting 4K video will work more efficiently with U3 speed cards, but for intro-level SLRs and point-and-shoots, U1 is often sufficient.

It can also be helpful to check the specifications for your camera to see if one speed of SD card or another is preferred by your camera’s manufacturer. Because cameras are constantly increasing in capability and resolution, it’s always a good idea to purchase the best available cards for futureproofing.

UHs 1 vs Class 10

Class 10 is the top speed available for an older type of SD card tech. Since 2009, UHS technology has become more common. It uses a newer data bus tech found in contemporary cameras. In order to use a UHS card, your camera must feature UHS technology. As far as write speed, UHS 1 and Class 10 are equally fast, with a minimum write speed of 10MB/s. Because the speed is identical, the choice of UHS1 vs. Class 10 cards will come down to the type of card compatible with your camera.

U3 vs Class 10 vs U1 SD Cards

U1 and U3 cards are compatible with the UHS transfer bus used in newer devices. Sometimes, you will also see a card rated with both U1 and Class 10. That means that when the card is used on a standard high-speed data bus, it will perform at Class 10 speed, but when used on a UHS bus, it will perform at U1 speed. As mentioned above, the speed for both of those circ*mstances is generally 10MB/s.

At that speed, U1 and Class 10 cards are both well suited for pro-level still cameras shooting RAW photos, and HD video recording at up to 1080p. This is a great speed to purchase if you’re looking for a balance between compatibility with your current equipment and future usage as well.

For 4K-capable cameras and larger resolution cameras that can shoot in high-speed burst shots, U3 is generally the safest bet for consistent, fast performance with zero lag.

Other SD Card Classes

Class 2

These cards are the slowest class currently available and are best suited for consumer-level point-and-shoot cameras, audio recording, and low-resolution SD video recording.

Class 4 & 6

The “middle of the road” in terms of speed, these cards will work well with still cameras shooting jpeg files and some very light HD video recording at 720p.

SD Card Security Considerations

No matter how much storage and speed you get from your SD Cards, it’s vital to have a system for protecting your data from physical dangers, time-related degradation, and data theft.

The size of SD cards makes them easy to store, but it also makes them easy to misplace. Consider the potential hazards when planning your storage and protection systems.

As you shop, make sure to invest in well-reviewed SD cards from reputable manufacturers. Top brands in the photography industry have a vested interest in offering lasting, high-quality SD cards that won’t cause widespread data loss.

Disable Write Protection

The only moving part on an SD card is the toggle switch on the left side that activates and deactivates write protection. If you’re ever worried about accidentally formatting an SD card that contains important data or footage, you can move the switch into the locked position.

Only full-sized SD cards contain the write-protection switch, so if you’re hoping to write protect a microSD card, you’ll need to use software to keep your data from being overwritten or deleted.

If you notice that your toggle switch becomes overly stiff or loose, it may be time to replace your card.

Password Protect

Though it is possible to password-protect an SD card or microSD card just like any other flash drive or hard drive, it usually isn’t a built-in feature. You’ll need to use encryption software with your Windows, iOS, or Android device.

Windows 10, 8, and 7 come with a software tool called Bitlocker that makes SD card encryption relatively easy, but you will need to format your card before encrypting so make sure you do this when you first purchase a new card. Android devices make it easy to encrypt external SD cards from the Security Settings menu, but the process varies depending on your device and system version.

Smart SD Cards

Smart SD cards are microSD cards with built-in SE and NFC capabilities. They feature similar technology to the contactless chip in your credit or debit card. They’re not necessarily appropriate for use in cameras and camcorders, but Smart SD cards are great for cellphone use.

With an onboard Smart SD card, you can use your phone for contactless payment with merchants, transit systems, and for secure entry with NFC-controlled door locks.

If you’re a photographer hoping to upgrade your mobile workflow with a Smart SD card, one great alternative is a WiFi-enabled SD card. This allows you to access your images with your smartphone or laptop with an integrated app.

SDIO Cards

SDIO cards are unique, and they’re kind of like a hybrid between SD cards and a mini computer. They offer both storage of data and computing or app functionality. SDIO cards can connect to Bluetooth adapters, GPS receivers, and a range of other devices.

SDIO cards haven’t gained popularity because they don’t work with just any SD card slot. Also, any of the devices that would utilize them, such as smartphones, have other methods of providing Bluetooth and GPS technology.

How Often Should SD Cards Be Replaced?

You should replace SD cards at the first sign of problems, or every 2-3 years of regular use. That’s because SD cards are prone to physical damage and wear and tear from use. They’re an excellent temporary storage solution, but only for capture and transfer to another device like a hard drive.

Here are a few situations to watch out for.

Physical Damage

While it’s painful to replace an expensive, high capacity card like an SDXC UHS-ii or a Samsung EVO Plus card, losing images after a shoot is even worse. Replace your card if you notice warping, splitting or separation of the sides, scratches or gouges on the contact points, or punctures, creases, or damaged dividers between contact points.

Degradation Over Time

Many people ask if cards degrade over time. If you format your cards correctly in-camera and take good care of your memory cards, they should last for a few years of use. That doesn’t mean, however, that memory cards are a good long-term storage solution for your photos. SD cards won’t hold data longer than about 5 years at most, so they’re best used as temporary storage.

How to Choose an SD Card: Bottomline

Choosing the right SD card for your device is crucially important to ensure that you’re getting the best performance out of your device, and also prevent any kind of hiccups or data loss. A card too small could fill up and leave you without any free space when you need it most. A card too slow could cause your device to choke when attempting to write files and potentially cause those files to be lost forever. Know your needs, find the right card, and your device will thank you.