What is uhs 2?

Nowadays, you'll find SD cards come in all manner of different shapes and sizes, and can be slotted into plenty of devices from cameras and smartphones to handheld games consoles like the Nintendo Switch. The world of SD cards can be a confusing one, with different speed ratings, sizes and capacities. Buying SD cards can be tricky, but with the right know-how, you'll be able to pick out the right SD card that suits your needs. Here's how to choose an SD card.

READ NEXT: Our pick of the best microSD cards

Nintendo's handheld/console hybrid, the Nintendo Switch, is a memory-hungry machine and it'll need some extra storage if you're planning on picking up as many great games as possible. Shipping with only 32GB of onboard storage, you'll run out of space pretty fast. Unlike most consoles, however, micro SD expansion is on the cards, but which is the best microSD card for your Nintendo Switch?

What with the Nintendo Switch supporting cards up to 2TB, there's plenty of different sizes to choose from. Obviously, prices skyrocket when you're looking at the higher end of the scale, so if you haven't got a whole lot of cash after buying the thing, perhaps get something small - 64GB or similar - for the time being. The biggest thing to look out for is that UHS-1 speed rating. There are official Nintendo-branded Switch micro SD cards doing the rounds, but they're bloomin' expensive, so here's our pick of the best SD cards for your Nintendo Switch.

As SD cards have begun to physically shrink down in size over the years, the SD card can be considered the ‘full-size’ variant. It’s typically what is used in most modern digital cameras and nearly all laptops will come equipped with an SD card reader slot.

Where things can become confusing is when you see ‘SDHC’ and ‘SDXC’. The first stands for ‘Secure Digital High Capacity’. This was initially introduced to cover SD cards with a capacity above 2GB and below 32GB. The latter stands for ‘Secure Digital eXtra Capacity’, which go far beyond 32GB in size. You can buy SDXC cards with a whopping 2TB of storage.

SD, SDHC and SDXC all physically look the same, therefore they’ll all fit in a regular SD card slot. Problems might arise depending on the device you’re looking to use them in. Older devices that pre-date SDXC’s introduction might therefore not be compatible, so be sure to check your product’s specifications. Devices are backwards compatible, so an SDXC-compatible device can use SDHC and SD cards. An SDHC-compatible device can use SDHC and SD cards, but will not be able to use SDXC cards.

The MiniSD was the first miniaturisation of the SD card and is around half the height of the original SD card. You can also find miniSDHC cards, which expanded storage to 4GB. Again, you’ll need to make sure your device specifically supports miniSDHC rather than just miniSD. The miniSD card never gained much traction, however, so devices that use it are relatively uncommon. Often, miniSD cards will come with an adaptor that can convert it into a full-size SD card, which makes it easier to use with laptop card readers.

The microSD is the smallest version. You might have also seen it referred to as TransFlash or abbreviated as a TF card. MicroSD cards, as the name implies, are physically tiny and came about predominantly to be used in smartphones that would benefit from a much smaller card.

Like the full-size SD card, there are also microSDHC and microSDXC variants that expanded the storage beyond the initial limitations. Right now, the largest microSDXC available is 128GB, which isn’t as much as the largest SDXC card but then you’re limited by the physical size of the card. When buying a microSD, microSDHC or microSDXC card you’ll usually get a full-size SD card adaptor as well. Again, SDXC-compatible devices will be backwards compatible with microSDHC and microSD cards, and microSD cards can be used in microSDHC devices.

The next area of confusion is around speed classes. These are how different SD, miniSD and microSD cards are rated in terms of read and write speeds. These are important particularly when the cards are used in camcorders or action cameras as the speed of the card will limit the video resolution and bit rate you’re able to record. High-resolution and high bit rate video requires a lot of data to be written to the card very quickly. Stills cameras with high resolutions and fast burst shooting will also take modern cards to their limits.

The SD Association devised a way to standardise the speed ratings for different cards. These are defined as ‘Speed Class’ and refer to the absolute minimum sustained write speeds. Cards can be rated as Class 2 (minimum write speed of 2MB/s), Class 4 (4MB/s), Class 6 (6MB/s) or Class 10 (10MB/s). It’s important to note that these are the minimum, so it’s entirely possible a card can achieve faster speeds but these give you an impression of the least you can expect.

Many SD card manufacturers will also list a specific speed alongside the Class rating. This means a card can be Class 10 but also be listed as ‘up to 80MB/s’. The wording is important, as that’s the best you can expect but not necessarily what you’ll always achieve. You might also see a description such as ‘533x’. This refers to a multiplication of the speed of an old CD-ROM (150KB/s). So in this case 533 x 0.15 = 80MB/s (as there are 1,000KB in a MB). On any type of SD card, the Class rating is denoted by a number inside of a C symbol.

The next rating is the UHS Speed Class. This stands for Ultra High Speed and refers to minimum sustained writing performance for recording video. UHS came about due to 4K-capable video devices needing faster write speeds.

The SD Association has two UHS Speed Classes, UHS Speed Class 1 and UHS Speed Class 3. UHS Speed Class 1 supports a minimum 10MB/s write speed, whereas UHS Speed Class 3 supports at least 30MB/s write speed. The UHS Speed Class is denoted by either a 1 or 3 inside of a bucket U symbol. As a rule of thumb, 4K-capable camcorders will usually require at least a U3 rated SD card.

Things get a little more confusing as UHS Speed Class-rated devices will also use one of two UHS Bus Interfaces that indicate the theoretical maximum read and write speeds. They’ll be listed as either UHS-I or UHS-II to show which interface is used. UHS-I devices have a maximum read speed of 104MB/s, whereas a UHS-II card has a maximum read speed of 312MB/s. Note that unlike the UHS Speed Class, these are not sustained speeds.

It might sound obvious, but the safest way to make sure you buy the correct card is to first consult your product's user guide or specifications, at least to be sure if your device takes full-size SD or microSD cards. Checking before you buy an SD card is particularly important if your device has specific requirements, such as many 4K camcorders. These will usually explicitly state what type of memory card is required in order to record at the top resolution or bit rate. The Sony FDR-X1000V action camera, for example, clearly states that it needs a Class 10 U3 microSD card in order to record in 4K.

If you're not recording in 4K, the speed might not be so important. A faster-rated card will still be useful if you're using the card to expand the storage in a smartphone or laptop, as a faster read and write speed will make it more responsive. Faster cards in a still image camera will also mean being able to take more or faster photos in burst mode, as these can be written to the card far quicker. Class 10 cards are usually not much more expensive so it's worth paying the extra.

It refers to something called ultra high-speed bus, which in turn refers to the interface between the card and the device. So far, there is UHS-I and UHS-II. There is a specification of UHS-III, but I’ve not seen any cards actually turn up using that yet.

UHS-II is the newer, and potentially faster, system but adoption is still not widespread. And a UHS-II isn’t necessarily guaranteed to be faster than every UHS-I card in practice. While it wasn’t always true initially, the current fastest SD cards are UHS-II (when used with a UHS-II compatible host, that is).

The UHS-I and UHS-II specifications are designed to be backward compatible. That means that you can use a UHS-II card in a device that’s compatible with UHS-I and vice versa. But if you do so, you’ll be limited to the lower spec, in this case UHS-I. That is the general intention, at least. But it gets a little more complicated, because there are different implementations of UHS-I that have different speeds. Some cards fall back to a slower UHS-I spec; better cards fall back gracefully to a UHS-I spec known as SDR104. Unfortunately, that particular part of the card’s capabilities is rarely specified in either the packaging or the technical specs.

But in many cases, it frankly doesn’t matter which you get. But that’s simply because the cameras and devices that can take full advantage of UHS-II are only just starting to become available.

And some that are UHS-II compatible can be a bit quirky. For instance, the FujiFilm X-Pro 2 camera has two SD slots. But only one uses UHS-II. So if you put a UHS-II SD card in the slot that has the UHS-I interface, you’ll be limited to UHS-I speeds.

But if you have a device that does use the UHS-II interface–and the technical specs or instruction manual will say so if it does–then there’s a good chance you’ll get better performance out of a UHS-II card.

One common device where this can become an issue is with memory card readers. Most of the card readers currently available support UHS-I cards. UHS-II cards will work, but they’ll be limited to UHS-I speeds. There are some card readers that do support UHS-II, such as the Lexar SR2 reader or the SanDisk Extreme Pro reader, but you can’t assume that every card reader does.

There are two ways to tell the difference. The first is obvious: look at the label or packaging. They’ll have either UHS-I or UHS-II, or sometimes just I or II. Technically, it should be Roman numerals, but you’ll sometimes see it incorrectly written as a number 1, like UHS-1.

You can also tell them apart by looking at the cards themselves. UHS-I cards have a single row of pins on the back. UHS-II cards have two rows. In this example, both of these are SanDisk Extreme Pro cards, just different generations.

The UHS-II code isn’t the only new code you’ll see on some microSD and SD cards. There’s also a new code that relates to suitability for recording high-resolution video. U1 and U3 have been around for a while; the new addition is V30.

All of these are speed classes aimed at recording high-resolution video. And they’re a separate designation from the UHS-I vs UHS-II one. I have more information on microSD speed classes here.

Here are a few other related tools I’ve put together that can be useful when working with memory cards and data rates.

Another related and common calculation that often needs to be done when working with memory cards is converting the convention for measuring video bitrate (Mbps, Mb/s, or megabits per second) to the convention for measuring the speed of memory cards (MBps, MB/s, or megabytes per second).

So I’ve put together a simple calculator for that separately. You can find it here:

If you’re trying to figure out what size memory card to buy, it can be useful to know how much video footage from the camera you can fit on a card. Here are a few tools that can be useful for that:

Here are some related posts for making sense of memory cards and working with them.

One of the more complex features the SD Association has released is Ultra High-Speed (UHS) bus interface. Evolving from normal SD card speeds (High-Speed), UHS SD cards has increased the potential data transfer speeds to meet the demands of modern high-speed devices.

What is Ultra High-Speed (UHS)?

Ultra High-Speed (UHS) is the new generation bus interface for SD cards. Succeeding the regular high-speed specification, UHS was recently designed to support devices with higher capacity and speed requirements.

In addition to handling higher memory card capacity, UHS standard raises the bar for faster data transfer rates, increasingly important when shooting high-resolution videos and large, RAW format images. To meet high demands of modern devices, UHS specification includes three versions: UHS-I, UHS-II, and UHS-III. These range in speed from an impressive 104 Mb/s to a jaw-dropping 624 Mb/s.

Differences between UHS-I, UHS-II, and UHS-II

UHS-I bus interface, with transfer rates up to 104 Mb/s, debuted as the first upgrade from normal, high-speed specification.

Next, came UHS-II, which bumped up the speeds to 312 Mb/s. Perhaps the most prominent difference from its first version, was the added 2nd row pins, which uses Low Voltage Differential Signaling (LVDS) technology to allow higher transfer rates.

Most recently, UHS-III specification was announced in earlier 2017, doubling previous UHS-II rates for insane data transfer speeds up to 624 Mb/s. UHS-III specification carries two lane, LVDS technology and uses new QR (Quick Recovery) function for improved power management to reduce its transition time from Dormant to Active. This optimizes your camera's power consumption, especially useful in shooting time-lapse, burst mode or extended videos.

What does this mean for me?

As UHS-III is a fairly new specification, it may be a while until most devices adopt the standard. However, many manufacturers, such as, Nikon, Sony, Olympus, Fuji and more, have already integrated UHS-II into their newer cameras and card readers.

Since Apple's shift to universal USB-C ports, newer MacBook models require Type-C dongles and adapters to connect other peripherals, including micro and SD cards. Many of these adapter's card slots do not support UHS-II or UHS-III standard yet. Even on newer 2017 models, iMac's native SD card slots are still not using UHS-II card readers. For now, only iMac Pro supports UHS-II SD cards. In other words, even if you are using an UHS-II SD card, you're still not able to fully experience upgraded speeds, unless you are using an iMac Pro.

With newer SD card specs introduced into the USB-C realm, we’re left with the question of how to connect UHS-I and UHS-II micro and SD cards to our Type-C devices.

Is there a solution for this?

Yes. With the Satechi Type-C UHS-II Micro/SD Card Adapter, now you're finally able to shoot brilliant 4K videos, capture high-resolution images and quickly upload to your Type-C device, using lightning-fast UHS-II speeds.

Transform your iMac's USB-C port into a UHS-II card reader slot, to fully experience the enhanced speeds of UHS-II standard. Or let our Type-C card reader travel with you! Keep one of our card readers in your camera bag, for viewing and uploading your exciting footage on-the-go through your Type-C smartphone, tablet or laptop.

The adapter is supported on virtually any Type-C Gen 3.1 device and compatible with both UHS-I and UHS-II micro/SD cards, for speeds up to 312 Mb/s. Interested? Pre-order on our Satechi site here. Available on August 2nd, 2018.

UHS-II cards have a second row of pins as compared to UHS-I, so they can be quite a bit faster, everything else being equal, BUT your camera needs to have slot(s) that also have the second row of pins AND their firmware needs to be able to take advantage of UHS-III to get the benefits.