Beginners Guide To Choosing MicroSD And SD Memory Cards

Beginners Guide For Memory Cards

I remember when I first got into photography back in 2006. My father bought me my very first DSLR camera with all of the accessories. But unfortunately I lost both the passion and free time to pursue it quite fast as I went to college. Well recently I decided to get back into it and bought a Sony A6000 mirrorless camera. But besides that, I also instantly met a completely unique confusion that I hadn’t had experienced before. I discovered that choosing a memory card has gotten much more complicated!

Sure I knew that my camera accepts an SD card but that’s simply the type. There were suddenly memory cards that looked completely identical but had different UHS writings and read/write speeds. It took me quite a while to research everything and even then I couldn’t completely understand which one I actually required. Which is why I eventually decided to figure out what all of the writings actually mean and write this guide for the rest of the beginners like me.

What Do The Markings Mean?

Back in 2006 there was only one type of SD cards and those are now called normal (SDSC). Later on there was a demand for memory cards that would support higher speeds. And that’s why SDHC and SDXC cards were created. These look exactly the same physically but they enable higher speeds. The HC stands for High Capacity (4 GB to 32 GB) and XC for Extended Capacity (larger than 32 GB). So these are simply an indication of the storage size. They have nothing to do with the speed.

SD Card UHS Types

Now what does have everything to do with speed is UHS. UHS stands for Ultra High Speed. It’s a type of bus interface that’s used with SDHC and SDXC type memory cards. It’s mostly because higher capacity and high speed data transfer usually goes hand in hand. That’s why they first created the UHS-I. As technology evolved and memory card capacity increased, they developed UHS-II and UHS-III to achieve even greater data transfer speeds. That’s basically the idea behind it. They bus interface is usually marked on the memory card with either I, II or III.

However UHS simply indicates the theoretical maximum speeds that the memory card is capable of. Technically speaking a UHS-I card can even beat a UHS-II memory card. It completely depends on the limitations that the manufacturer has set. That’s why there are also actual speed ratings that indicate the maximum read and write speeds that the cards support. Those are marked with Class 10, U1, U3, V30, V60 and recently revealed V90. These are the actual ratings that you should care about and I’ll go over them below.

UHS-I Interface

The UHS-I is the very first Ultra High Speed bus interface that was introduced for SD cards back in 2010. It increased the original maximum bus speed of 25 MB/s all the way to 104 MB/s. The actual read and write speeds are lower due to manufacturer set limitations and reading hardware. But the fastest UHS-I SD card (SanDisk Extreme Pro SDSDXXG) has been recorded to achieve 98.8 MB/s read speed and 90.5 MB/s write speed. It has the U3 speed class.

UHS-II Interface

The UHS-II is the second generation bus interface. It increases the maximum bus speed to 312 MB/s. Which is exactly 3 times higher than the UHS-I version. It was first introduced back in 2011 but widely adapted a couple years later. But nowadays you can find it everywhere. Especially among the higher capacity memory cards. There is also a physical difference between the two UHS versions. The UHS-II interface requires an extra row of pins that visible on the microSD and SD memory cards. Which is why you’ll also need a UHS-II compatible memory card reader if you want to use them.

But again that’s the bus speed and the actual read/write speeds mostly depend on the manufacturer and the type of reader you use. The absolutely fastest UHS-II SD card (ProGrade PGSD128GBCJNA) has achieved 282.6 MB/s read speed and 254.4 MB/s write speed. It belongs in the incredibly fast V90 speed class.

UHS-III Interface

The UHS-III bus interface was first introduced for SD cards in 2017 at CES. It boosts the bus speed up to 624 MB/s. Which is 2 times faster than the UHS-II version. It also reduces the time it takes for the SD card to switch between active and power saving states. This type of SD cards are currently only available for professionals. You won’t find any UHS-III SD cards from any online stores. Simply because the technology is still incredibly new and the UHS-II supported transfer speeds are more than enough for consumer cameras. That’s also why I can’t provide any real life examples currently.

Speed Classes

As I mentioned before, UHS simply provides the information about the type of bus interface the memory cards have. Which does also give you an idea of the maximum transfer rate that the card can handle. That said, manufacturers limit those speeds. Which is why you should also pay attention to Speed Classes. They are the real indicators of what data transfer speeds you can expect. So let’s take a look at the class types and who they are best for.

SD Card Speed Class

Class 2, 4 and 6

These three are the lowest speed classes available. Class 2 has a minimum write speed of 2 MB/s, which was essentially designed for SD videos. The 4 and 6 are a bit faster at 4 MB/s and 6 MB/s. And they can be capable of saving 720p and 1080p videos, however, only certain frame rates. Which makes them quite unreliable. That’s why I don’t really recommend getting a memory card that belongs in 2, 4 or 6 class. I once bought one for super cheap only to store music on it for my car. So you can technically use them for that.

Class 10

Class 10 is the lowest speed class that you can easily find from any store. That’s also one of the reasons why I don’t recommend getting anything lower than that. Plus there’s really no difference in price anymore. The class 10 indicates a minimum write speed of 10 MB/s. This is enough to record 1080p at lower frame rates. Which again isn’t that reliable when it comes to recording videos. But you can definitely use it for photography. This is actually the minimum speed rating that most modern cameras accept.

U1 & U3

U1 and U3 are the two most popular speed classes for SD and microSD cards. The U1 also indicates a minimum write speed of 10 MB/s but its also optimized better for recording HD and 1080p videos. U3 on the other hand is much faster with a minimum write speed of 30 MB/s. This is capable of handling 4K videos. That’s why most GoPro action cameras recommend getting MicroSD cards with a U3 speed class.


V60 is a speed class that’s much harder to find. It indicates that the memory card has a minimum write speed of 60 MB/s. That’s enough to record both 4K and 8K videos. There are also some high end cameras that require V60 memory cards because they record in a ultra high bitrate. The Panasonic GH5 is one of those.


V90 is the newest and highest rating for memory cards. As you can probably tell from the name by now, the class is rated to have a minimum write speed of 90 MB/s. These type of cards are specially aimed at professionals. They are created to handle 8K videos and cameras that are capable of that, are quite rare. Which is why you won’t find any V90 memory cards from a random store.

So Which Type To Choose?

Okay so the first thing you need to decide is what you are going to be using it for. Are you going to be using it simply to take photos or are you going to be recording videos as well? Or maybe you are just going to use them to store data, like me with my cars music SD card. And if it’s videos then what are the highest resolutions that your camera supports. These are basically the key specs that you have to pay attention to as they set the requirement for the speed classes.


If you are just getting started with photography then I recommend looking at memory cards that are at least UHS-I and have a speed class of U1. That’s pretty much the basic requirement. Anything above that will only increase the time it takes to transfer the photos to your computer. That’s one of the reasons why professionals and hobbyists sometimes prefer faster cards. But generally speaking U1 is enough.


Now if you are going to be recording videos with either a normal camera or an action camera, then you need something a bit faster. Most modern cameras are capable of recording in a 4K resolution. Which is why you should go with a U3 speed class. These can handle both the 4K resolution and also 1080p at higher frame rates. As far as UHS goes, you can go with either UHS-I or UHS-II. It completely comes down to how large the videos are going to be. If you are going to be doing like vlogging, then I’d personally go with UHS-II U3 memory cards. Simply because it will take less time to transfer the videos to a computer. That’s why you should also take a look at the manufacturer specified read/write speeds.

Nintendo Switch

For Nintendo Switch, it’s most important to go with a microSD card that has a high capacity. Go with something that has at least 64 GB of space. Anything less than that will fill up quite fast. The speed however, isn’t that important. What I’d look for is a simple UHS-I memory card with a U1 speed class. You won’t need anything beyond that. You could also get away with Class 10 but they are much harder to find nowadays. Plus there’s really no difference in price anymore. So you may as well just go with U1.