Memory cards have evolved quite a bit in the short time since their development and when you go to buy a memory card today, you may find yourself overwhelmed with all the different markings and codes written on them. In this post, we’ll talk about two common SD card markings: UHS 1 vs Class 10.
UHS 1 Vs Class 10
Interestingly enough, comparing UHS 1 to Class 10 is like comparing apples to oranges, since both UHS and the Class denote different properties of the memory card.
UHS is the abbreviation for Ultra High Speed and stands for the kind of connection between the SD card and the device, whether it’s a camera, card reader, phone, or any other device.
UHS 1 is an evolution from UHS. UHS 1 is capable of transferring data at up to 104 MB/s. The earlier UHS was capable of just 1/4th of that.
However, here’s where things get muddy. Just because the bus can transfer data at 104 MB/s does not mean that the card can actually read or write data at that speed! The read and write speed is usually up to 10 times slower.
The speed used for writing data is denoted by the Class.
So essentially, a card that is rated to be Class 10 and UHS 1 can transfer, read, and write data at around 10 MB/s.
More about SD card markings
Now that we’ve covered the difference between UHS 1 and Class 10, let’s talk about the different kinds of markings you’d find on SD cards.
As you saw above, many cards are denoted as UHS 1 or UHS 2. UHS 1 maxes out at 100 MB/s, and UHS 2 is closer to 312 MB/s transfer speeds due to a higher quality bus system.
However, the transfer speed is limited by the read and write speed, which is where Class comes in.
- Class 2: 2 MB/s
- Class 4: 4 MB/s
- Class 8: 8 MB/s
- Class 10: 10 MB/s
Here’s where things get messy. It’s not completely clear whether UHS-1 and UHS Class 10 are the same thing, or they’re different.
If your card has the UHS-1 symbol, which is the letter I in bold capital letters, it indicates that this is UHS-1 and has the bus speed of up to 104 MB/s. Remember, this is the bus speed, not the write speed or read speed.
Next you have UHS Speed Class 1, which is a 1 inside a U, which means that the transfer speeds are up to 10 MB/s.
If this seems confusing, it is! These standards were developed by the SD Association, and to be honest, I have no idea what they were thinking before making such a mess of things.
This card has a marking for UHS 1 and Class 10
This card has a marking for UHS 3 but no Class marking.
Is it all just a marketing gimmick?
To a certain extent, yes, UHS bus speeds and speed classes are indeed marketing gimmicks.
Instead of relying on manufacturer speed ratings, it’s better to dig up independent testing results as they’re far more accurate representations of what would happen in regular applications.
For example, Sandisk states that their UHS-1 cards can get
…up to 30 MB/s read speed based on internal testing
The terms up to and internal testing pretty much skew the results as anything between 1 and 30 is up to 30.
Basically, it seems like marketing departments just have a lot of leeway to cleverly word their product descriptions and specs in a way that makes the speed of the SD cards seem very high, but you may not really see that in reality.
Putting the confusion to rest
All things said and done, it’s safe to say that it’s pretty certain that UHS-1 and Class 10 are equivalent because they can achieve the 10 MB/s speed.
Class 10 is the minimum requirement for most video cameras(action cameras and even smartphones if you’re using them for a lot of video), as anything slower will result in choppy video from the slow transfer rate.
The SD association could have done a better job of not caving into marketing speak and standardizing the terms so they would be easier to understand and interpret.
Frequently asked questions
Is UHS 1 or 3 better?
According to the SD association, UHS 1 is equivalent to Class 10 as it can sustain 10 MB/s transfer speeds. In the table they have on their site, UHS 3 has no equivalent Class rating, but they state that it can sustain up to 30 MB/s transfer speeds. Up to is the key word here.
Which is better, Class 1 or Class 10 SD card?
Higher Class ratings means the read and write speed will be higher. For applications where you require high speed data transfer, such as gaming or photography, a higher Class card will be better.