- Class 2 - 2MB/s
- Class 4 - 4MB/s
- Class 6 - 6MB/s
- Class 8 - 8MB/s
- Class 10 - 10MB/s
- Class 1 - 10MB/s
- Class 3 - 30MB/s
- Type A, which has one PCIe 3.0 pipeline that results in a maximum speed of 1GB/s
- Type B, which has dual PCIe pipelines that results in a maximum speed of 2GB/s
- Type C, which has four PCIe pipelines that results in a maximum speed of 4GB/s
- SD - This is the first kind of SD card and it had storage capacity up to 2GB. Their size and shape became the norm for modern SDHC and SDXC cards.
- microSD - These cards are smaller versions of SD cards that are often used in mobile devices like smartphones and tablets, though some cameras use microSD. These cards offer up to 16GB of storage and speeds up to 8MB/s. There are also microSDHC and microSDXC cards that offer greater storage and speed options.
- miniSD - These cards are larger than microSD, but smaller than normal SD cards. However, they offer the same storage capacity and speeds as microSD cards. Again, there are miniSDHC and miniSDXC card options that provide more storage and better speeds.
- SDUC - SDUC stands for Secure Digital Ultra Capacity. It is a form of SD card that is the same size as SDHC and SDXC cards, but has a much higher storage capacity. In theory, these cards could hold up to 128TB of information. These cards are not common.
- Compact Flash - CF cards were developed in the 1990s as a more reliable form of memory card due to their larger size and robust build. However, they were slow and have since been replaced by much faster options, like CFexpress.
- CFast - CFast cards came along as an improvement to CF cards. Unlike CF cards, which used a slow Parallel ATA/IDE bus, CFast cards use the much faster Serial ATA bus. However, CFast cards never really caught on and were only supported in a handful of cameras, like the Canon 1D X Mark II.
- XQD - Introduced in 2010, XQD was a new, faster format thanks to its reliance on the PCIe interface. It basically replaced CompactFlash and CFast cards. XQD cards are slightly smaller than CF and CFast cards. Though these cards were the fastest available at the time, they were not widely adopted. CFexpress cards are viewed as superior and will replace XQD as the high-end standard for memory cards.
think we can all agree that memory cards are one of the most important photography accessories you can have in your camera bag. After all, it’s not like you can go out and shoot photos without a memory card in your camera!
But despite their importance, I find that a lot of folks don’t really know what to look for in a memory card. In fact, one of the most common questions I get is asking what all the numbers and figures on a memory card actually mean.
With that in mind, I’ve put together this quick memory card shopping guide. We’ll discuss different card types, read and write speeds, capacities, compatibility issues, and much more.
Memory Card Types
When shopping for a memory card, your first task is to get the type of card that’s compatible with your camera.
This means that I can swap SD cards between my two cameras, but I can only use CFexpress cards in the R5.
Let’s talk about these and other types of memory cards in more detail.
These cards are extremely popular and are used by all sorts of different cameras, from DSLRs to full frame mirrorless to compact cameras.
Though there are many different types of SD cards, the most common today are SDHC (Secure Digital High Capacity) and SDXC (Secure Digital Extended Capacity).
Typically, cards with greater than 4GB of capacity are considered SDHC cards. SDXC cards, meanwhile, start at 64GB and extend up to 2TB of storage space.
SDHC cards come in five different classes, each of which indicates a different minimum speed, as shown below:
SDXC cards, on the other hand, come in two different classes. Again, the class of the card indicates its minimum speed:
So, SDXC cards not only offer larger storage capacities but they also offer faster read/write speeds than SDHC cards. However, the fastest SD cards max out at around 624MB/s. This pales in comparison to the speed of CFexpress cards.
CFexpress cards are the newest type of card and they offer the largest storage capacities and speeds currently available. That’s why high-end cameras like my EOS R5 have a CFexpress slot - cards like this are needed to take advantage of modern camera features like recording 8K video or extremely fast burst rates for still images.
These cards are faster because they use PCIe 3.0. This is the same interface used by SSD drives in many laptops and desktop computers. As a result, the fastest CFexpress cards offer maximum speeds up to 4GB/s. That’s about the same speed of a SSD on a high-end laptop.
CFexpress cards come in three versions:
At present, no cameras support the Type C CFexpress cards because they are much larger than Type A and Type B cards.
Type A cards are the smallest, and are slightly smaller in their form factor but thicker than an SD card.
Other Types of Memory Cards
There are plenty of other types of memory cards, but they are either not as popular as SD cards or will likely be replaced by CFexpress cards as they become more widely adopted.
Here’s a quick rundown of some of these cards:
Memory Card Features
After you determine the type of memory card you need, you have to consider the memory card features that are available. This includes memory card sizes and speeds.
Memory Card Sizes
The size of a memory card refers to its capacity. Back in the day, capacity was measured in megabytes. However, today’s cards are often found in gigabytes and even terabytes.
The size is indicated on the front of the card, as shown in the image above. It is easy to spot because the size of the font is usually quite large and the number is followed by MB, GB, or TB.
The size of the card you need depends on your specific workflow. Obviously, professional photographers will want much larger capacity cards to accommodate the number and size of images files they create. You’ll usually find pros carrying around cards like my ProGrade CFexpress Type B 650GB card.
However, if you’re an occasional photographer that doesn’t shoot high-resolution images or rapid bursts of images, a smaller card, like a 16GB might suffice.
Memory Card Speeds
The speed that a memory card offers can vary greatly. Speed depends on a number of factors, including whether you’re referring to the read speed or the write speed, as well as the type of card you’re using.
On SD cards, speed is referred to as speed class. This defines the maximum speed that a memory card can provide. Additionally, memory cards are rated on their bus speed, which indicates the maximum bus speed the card can achieve. Bus speed is indicated by a UHS rating.
For example, my primary card for my EOS R6 is a ProGrade 128GB SDXC UHS-II card. It has a read speed of 300MB/s (1) and a write speed of 250MB/s (2), as shown in the image above.
As a UHS-II card, the maximum bus speed this card offers is 312MB/s. Compare that with a UHS-I card which maxes out at 104MB/s and a UHS-III card that maxes out at 624MB/s. Since this is a UHS-II card, it has the Roman numeral II on the front (3) to indicate it as such.
Also on this card are the Speed Class and the UHS Speed Class.
As you can see in the image above, Speed class is indicated by the number 10 with a partial circle around it (4) and UHS Speed Class is indicated by the number 3 with a U-shape around it (5). In this case, a 10 Speed Class indicates a guaranteed minimum write speed of 10MB/s while the UHS Speed Class indicates a minimum 30MB/s write speed.
The last number to discuss is Video Speed Class, which is indicated by a number like V90, as you can see in the image above (6).
Video speeds are derived from the minimum write speed. This means that a V90 card like this one can write video data at 90MB/s. This is the fastest video speed class currently available, with V6 representing the slowest.
You can see the read/write speeds indicated on CFexpress cards as well. As shown in the image above, my ProGrade 650GB CFexpress card has a read speed of 1700MB/s and a write speed of 1500MB/s.
Also noted on the front of this card is the type - CFexpress Type B - and its capacity, which is 650GB.
Memory Card Compatibility
It’s important to note that the card type, sizes, and speeds will determine whether a card is compatible with your camera or not.
In some cases, cameras have a single card slot, like my old EOS R. In other cases, they have dual card slots, like the two SD slots on my EOS R6. In yet other cases, a camera can have two slots with each being a different type, like the CFexpress and SD slots on my EOS R5, as shown above.
If you aren’t sure what kind of card(s) your camera takes, reference the owner’s manual before purchasing a card.
Memory Card Readers
In general, the technology used in most memory card readers is the same. This means that apart from bargain-basement knockoffs, most card readers will perform about the same.
Personally, I have two ProGrade readers. The first is the ProGrade CFexpress PG04 Thunderbolt Card Reader. I use this as my primary card reader because the Thunderbolt connection allows me to take full advantage of the card’s speed.
But when I’m traveling, I take the ProGrade PG-05.5 CFexpress and SDXC Dual Card Reader. This allows me to use one reader for both types of cards I carry. However, since it is USB-C and not Thunderbolt, you don’t get the crazy-fast downloads.
Again, though I prefer ProGrade card readers, you can find a solid card reader from many different brands. Just be sure that you get a card reader that is compatible with the type of memory card(s) you use.
Memory Card Recommendations
In addition to getting lots of questions about memory card speeds, memory card numbers, and memory card types, I get tons of questions about which memory cards I use and recommend.
If we went back in time five or six years, I’d recommend SanDisk memory cards. They were my go-to cards for years and years until I experienced a failure. This was my first experience with a failed card, and as is often the case, you only need one bad experience to start looking for greener pastures.
I then started using Lexar cards, which went well for a while, but then I experienced another card failure - this time, the Lexar card fragmented. Again, I was left looking for a better, more reliable alternative.
Right around the same time, I was hearing a lot of good things about ProGrade memory cards. Since I’d experienced failures with SanDisk and Lexar, I decided to see if all the hype about ProGrade was deserved or not.
The first ProGrade card I picked up was the 64GB SDXC UHS-II card. I then got a 128GB SDXC UHS-II.
It didn’t take long for me to realize that all the pros I’d talked to were right about these cards - they are blazing fast (both in terms of writing data to the card and pulling data off to my computer) and they are ultra-reliable.
Given my experience with these cards, I stuck with ProGrade when I upgraded my camera to the EOS R5. I got their 512GB CFexpress Type B Gold card which offers 1700MB/s read speeds as well as the 650GB CFexpress Type B card I spoke of earlier, which offers 1700MB/s read speeds and 1500MB/s write speeds.
While I still have some of my older Lexar and SanDisk cards, they are really only in my bag for “in case of emergency” purposes. My ProGrade cards have been such a joy to use that they have definitely become my “daily driver” cards - and I highly recommend that you use them as well!
I’ve been with ProGrade for about a year now and have used both SD and CFexpress cards in various camera systems. I have never encountered a problem. The read/write speeds are absolutely insane. The cards are well made, durable, and incredibly reliable. These are the exact features that you want in a memory card!
I get that some memory cards seem like they’re eye-poppingly expensive. However, this is one of those things where you get what you pay for. In other words, think of getting a memory card as an investment, something that will work for you for the long-term and provide you with reliability and durability that you can trust.
There is nothing worse than losing image or video files due to a memory card malfunction. If you want the utmost in reliability, my recommendation to you is to find the right ProGrade card for your camera system and your budget.