What are UHS-III Memory Cards? And Should You Buy One?

UHS-III was one of several competing up-and-coming technologies to make memory cards faster so as to keep up with the needs of capturing 8K, 360-degree, and virtual reality footage. But there’s no point in rushing out now and buying a UHS-III card (even if you could).

A faster memory card = high-bitrate capture

Memory cards that can hold a terabyte or two are becoming increasingly common and even affordable. That’s a lot of storage space, regardless of whether you’re shooting photos or video. And the next generations of memory card specs can theoretically hold exponentially more than that.

So the competitive frontier has been shifting to speed. And it’s not just about speed now; it’s about memory card speed in the future.

And that’s crucial for understanding UHS-III. It’s not a technology that’s being used yet in today’s cameras. It has been developed with the needs of the next generation of cameras in mind.

A faster memory card won’t help you take better photos. But it does allow for increasingly better quality digital capture. Higher resolution video with less compression. Larger images with more RAW data capture and less compression. When it comes to memory cards, speed matters for recording large amounts of data to the card quickly. For things like real-time capture of high-resolution video, or a long burst of rapid high-resolution RAW photos, for example. If a memory card can’t write the data fast enough, it’s going to limit what the camera can send to it. Which is why specs like UHS-III are being developed, so that camera features aren’t shackled by memory card technologies that can’t keep up.

Key points of UHS-III

UHS-III was designed as a forward-looking specification for ever-more-demanding video and photography needs. It was developed by the SD Association as the next-generation spec. It is not used or relevant to other kinds of memory cards such as CFexpress (i.e., those developed by the CompactFlash Association).

It was introduced with the SD 6.0 specification by the SD Association in 2017. It’s specifically designed to cater to the burgeoning need for higher data transfer rates necessitated by 8K videos, 360-degree cameras, drones, and the advent of high-speed wireless communications such as 5G (and presumably 6G) and the latest Wi-Fi standards.

UHS-III key features & innovations

• Unprecedented Speed: UHS-III sets a new benchmark for data transfer, boasting theoretical speeds up to 624 MB/s, doubling what its predecessor, UHS-II, offered. This leap in speed is facilitated by a sophisticated bus interface that includes three differential signaling lanes, ensuring rapid data communication between the SD card and the device.
  
• Forward Compatibility: UHS-III maintains backward compatibility with UHS-I and UHS-II devices, ensuring that users can still benefit from its use in a wide array of existing devices, albeit at reduced speeds if the device does not support the UHS-III standard. But it’s important to note that that does not mean you can put a UHS-III memory card into a device that only supports UHS-I and UHS-II and expect the full benefit of UHS-III. The card will work, yes, but it will fall back to the lowest available UHS system in the chain. Put another way, a UHS-III card in a camera that supports up to UHS-II will only perform up to UHS-II speeds.
  
• Enhanced Bus Interface: It’s not only about speed. UHS-III introduces an enhanced bus interface with features like the Quick Recovery (QR) Dormant function, which significantly reduces the transition time from a low-power dormant state back to active use. This ensures efficient power management and quick accessibility when needed.
  
• Dual Range Full-Duplex Mode: With the addition of Range C and D, UHS-III supports full-duplex mode, eliminating the need for bus direction switching and enabling simultaneous read/write operations. This, coupled with “emphasis” technology, improves signal integrity and boosts transmission speeds to new heights.

But there’s a catch

While UHS-III theoretically offered significant speed gains, the industry’s rapid adoption of PCIe and NVMe protocols for memory cards, which were part of the competing SD Express standard, has largely sidelined UHS-III.

Camera and card manufacturers have mostly skipped UHS-III to embrace the higher performance ceiling and more established ecosystem of PCIe-based solutions.

In other words, UHS-III is, for all current practical purposes, a zombie spec that is unlikely to ever be adopted.

What does UHS-III mean for shooting photos & videos?

So what does this mean for photographers and videographers?

Two parts of this new technology are particularly important for capturing image data, whether that’s stills or video.

The first is the faster transfer speed. A maximum transfer rate of up to 624 megabytes per second (MB/s) means that high-bitrate 8K and 360-degree video have a lot more headroom. It’s important to note that that speed is megabytes per second. When translated to the megabits per second more traditionally used when referring to video bitrate, that’s nearly 5,000 Mb/s (4,992 Mb/s, actually). Most of the best video capture cameras available now use less than 600 Mb/s for their compressed modes. Some allow for a lightly compressed ProRes or even RAW capture that goes far higher than that — perhaps up to around 2,000 Mb/s. But UHS-III is built specifically to be able to handle that kind of capture handily. And, importantly, there is an area where the current generation of SD cards lags behind CFexpress cards, which is why some cameras will only let you shoot their highest-mode video if you’re using a CFexpress card.

Whether it’s shooting in burst mode, recording in 4K, 6K, or even 8K resolution, or transferring large files, UHS-III reduces wait times (or, more technically, latency), which decreases the overall time of data transfer operations. That, in turn, leads to better efficiency and a faster workflow.

The second is duplex mode. This allows for simultaneous read/write in separate lanes rather than waiting for one operation to finish before the next starts. This will allow for some extra possibilities for capturing high-rate burst photo modes, for example, as it can clear the camera’s buffer more quickly. It will also allow for concurrent streams, so cameras might be able to record two different kinds of video stream simultaneously, or cameras facing different directions (such as with 360-degree capture or augmented reality) being able to more easily record to the same endpoint.

Future-looking: “Future-proof” is overused, and when it comes to things like this it’s often a misnomer simply because of the rate of improvement and innovation in the image capture space. But UHS-III is certainly a forward-looking spec and is designed to keep pace with cameras that are likely to come out in the next several years.

Practical considerations

So this all sounds great! Should you rush out and buy a UHS-III card for your camera?

Nope. For a couple of reasons.

Firstly, good luck finding one. While the spec has been announced for several years now, as at the time of writing (originally February 2024, and revising in January 2026), there still aren’t any UHS-III consumer cards in the wild. They’re still not available, never have been, and likely never will be.

And there’s a very good reason for that: no consumer cameras support UHS-III yet. While the UHS spec is designed to be backward compatible, that’s only to the extent that it will work. You can put a UHS-III card in a camera that supports up to UHS-II and take photos. But you’ll only get up to UHS-II speeds.

For users aiming to future-proof their equipment for extreme data rates, the focus would be better spent on SD Express cards and compatible cameras. These are the solutions genuinely emerging in the consumer market and are better positioned to meet the demands of future high-resolution, high-bitrate capture.

And for larger cameras where the physical size of the memory card isn’t quite so critical, there’s already a much better alternative that’s very widely adopted: CFexpress (especially Type A and Type B). SD Express is designed to compete in this high-performance segment within the SD form factor, but CFexpress currently holds broader support in top-tier professional video and mirrorless cameras.

Related technologies

Memory card associations like the SD Association and the CompactFlash Association have vested interests in pushing the envelope. They want to be in on the ground floor as camera manufacturers’ research and development teams are looking years or maybe even decades into the future with development maps.

Somewhat confusingly, UHS-III is just one of several competing technologies. And that’s just counting those announced by the SD Association alone.

Others you might come across that are closely related include:

• SD Express (and microSD Express). This is a broader memory card update. Again, it’s focused on a speed, but it refers to a different kind of interface (and thermal management). And it comes with its own speed rating system. These are already turning up on the consumer market, but again, there’s no point using one in a camera that isn’t explicitly compatible with SD Express.
• SDUC. You’ve heard of SDHC and SDXC. SDUC is the next iteration of that. It stands for Secure Digital Ultra-Capacity, and it refers to the filesystem and storage space, not speed. It allows for cards with up to a whopping 128TB of storage space.