UHS-I and UHS-II are specifications for Ultra High Speed SD cards that support faster data transfer speeds than standard SD cards. UHS-I cards have a maximum data transfer speed of up to 104 MB/s while UHS-II cards can reach up to 312 MB/s. Choosing between UHS-I and UHS-II really depends on your use case and budget. UHS-II cards are faster but also more expensive. For most consumers, UHS-I cards offer a good balance of speed and value. Professional photographers and videographers who need to transfer lots of high resolution files may benefit from the extra speed of UHS-II.
What is UHS-I?
UHS-I stands for Ultra High Speed Phase I. It is an SD card specification that supports faster data transfer speeds than standard SD cards. UHS-I was introduced in 2009 as an upgrade over standard SD cards. UHS-I cards support data transfer speeds of up to 104 MB/s. This is over twice as fast as regular SD cards which top out around 40 MB/s.
UHS-I achieves these faster speeds through improvements in the SD card’s interface. It uses an additional row of physical pins and increases the clock frequency for data transfers. However, UHS-I cards still use the standard SD card communication protocol. They are fully backwards compatible with older SD host devices.
UHS-I Speed Classes
UHS-I cards are further divided into speed classes that indicate their minimum guaranteed speeds:
| UHS-I Class | Minimum Write Speed |
|---|---|
| U1 | 10 MB/s |
| U3 | 30 MB/s |
The U1 speed class supports a minimum sequential write speed of 10 MB/s. This is fast enough for recording full HD 1080p video. The U3 speed class has a minimum write speed of 30 MB/s. It is better suited for 4K video capture. The theoretical maximum speed of UHS-I cards is 104 MB/s. However, real-world speeds often top out around 90 MB/s.
UHS-I Uses
UHS-I SD cards offer a good blend of speed, value and compatibility. The faster transfer speeds make them better suited for:
– Recording HD and 4K video
– Continuous burst mode photography
– Transferring large files like RAW photos
UHS-I cards are commonly used in:
– DSLR and mirrorless cameras
– Advanced point & shoot cameras
– Android smartphones and tablets
– Action cams like GoPro
– Drones
For most consumers doing general photography and videography, a UHS-I card provides plenty of performance. The only caveat is that UHS-I requires a host device that supports UHS-I. But most digital cameras and mobile devices made in the last 5-10 years are UHS-I compatible.
What is UHS-II?
UHS-II is the second generation of the Ultra High Speed standard for SD cards. It builds on UHS-I and offers even faster transfer speeds. UHS-II was introduced in 2011 with maximum speeds up to 312 MB/s – triple the rates of UHS-I. But UHS-II cards achieve this increase through further enhancements to the SD interface.
First, UHS-II makes use of an additional row of physical pins. This expands the interface to 2 rows of pins compared to just 1 row on UHS-I. Second, it increases the data transfer speed by moving from a single lane to a dual-lane interface. This doubles the maximum clock frequency for data transfers.
UHS-II Speed Classes
Like UHS-I, UHS-II cards have defined speed classes:
| UHS-II Class | Minimum Write Speed |
|---|---|
| U1 | 10 MB/s |
| U3 | 30 MB/s |
However, these speed ratings are much lower than the maximum speeds which UHS-II is capable of. The UHS-II specification currently allows for speeds up to 624 MB/s using an 8-lane interface. But cards this fast have not yet been produced. The fastest UHS-II cards available today max out around 260-320 MB/s.
UHS-II Uses
UHS-II offers very fast transfer speeds but is currently only supported on high-end cameras and devices. UHS-II works best for:
– Professional/commercial photography
– Shooting RAW images and large file sizes
– 4K and 8K video recording
– Transferring data to/from external storage
UHS-II sees most use in:
– High-end DSLR cameras
– Expensive mirrorless cameras
– Broadcast camcorders
– External USB card readers
Very few smartphones and consumer devices support UHS-II. And UHS-II cards cost 2-4x as much as UHS-I cards with comparable capacities. For most amateur photographers, the extra speed does not justify the added cost. But for professionals who value maximum performance, UHS-II delivers.
Comparing UHS-I and UHS-II
Here is a direct comparison of the key specs and features between UHS-I and UHS-II SD cards:
| Feature | UHS-I | UHS-II |
|---|---|---|
| Interface | Single-lane | Dual-lane |
| Maximum clock speed | 50 MHz | 200 MHz |
| Maximum data rate | 104 MB/s | 312 MB/s |
| Speed classes | U1, U3 | U1, U3 |
| Backwards compatible | Yes | Yes |
| Common capacities | Up to 512GB | Up to 512GB |
| Price (USD) | $10 – $75 | $50 – $250 |
From this comparison, you can see that UHS-II simply builds on UHS-I. It uses additional interface lanes and higher clock speeds to achieve 3x faster transfer rates. But UHS-II is still backwards compatible with UHS-I host devices. The main tradeoffs are performance vs. cost. For most amateur photographers, UHS-I hits the sweet spot. But professionals who need the bleeding edge speeds will benefit from UHS-II.
UHS-I vs UHS-II – Key Differences
Here are the most important things to know when comparing UHS-I and UHS-II SD card standards:
Speed
– UHS-II is nearly 3x as fast with peak transfer speeds around 312 MB/s compared to 104 MB/s on UHS-I.
– But real-world speeds may be lower, around 200-260 MB/s on current UHS-II cards.
– For most users, UHS-I speeds of 80-95 MB/s are sufficient. Only pros routinely hit the limits.
Price
– UHS-II cards cost significantly more than UHS-I at around 2-4x the price per GB.
– A 128GB UHS-I card may cost $25 while a 128GB UHS-II card can be $100+.
– The price premium for UHS-II is difficult to justify for casual users.
Compatibility
– UHS-II cards are backwards compatible and will work in UHS-I devices, albeit at lower speeds.
– But you need a UHS-II compatible device to leverage the faster transfer rates.
– Very few non-professional cameras and devices support UHS-II currently.
Use Cases
– UHS-I offers a good balance of speed and value for general use including full HD/4K video.
– UHS-II excels at RAW, burst and high-res video like 8K, but few devices support it.
– Professionals who edit large files benefit most from UHS-II. Casual users do not.
UHS-I vs UHS-II – Comparing Real-World Speeds
The official speed ratings for UHS-I and UHS-II can be misleading when choosing between the two standards. In practice, there are several factors that limit real-world transfer speeds:
Bus Speed Limits
Many cameras cannot fully saturate the UHS-II bus. Many models top out around 260 MB/s even though UHS-II supports 312 MB/s. Older UHS-I cameras max out around 90 MB/s despite 104 MB/s being possible. The camera’s image processor and memory architecture can bottleneck speed.
File Size and Types
The file size being transferred impacts speeds. Large contiguous files like RAW images can reach peak transfer rates. But small compressed JPEGs only do a fraction of peak speeds. File caching also allows for burst speeds beyond what sustained transfers can do.
Card Controller and NAND
The SD card’s controller and NAND flash memory capabilities play a role too. Budget cards often have slower controllers that handicap performance compared to high-end cards. Lower-grade NAND can be slower as well.
USB Transfer Limitations
When transferring files from the SD card to a computer over USB, the USB speed also comes into play. USB 2.0 tops out around 35 MB/s, USB 3.0 around 625 MB/s. Many USB card readers for UHS-II cards still use USB 3.0.
Real-World Test Examples
Here are some real-world transfer speed tests that demonstrate the difference between UHS-I and UHS-II performance:
| Card | Test | Transfer Speed |
|---|---|---|
| SanDisk Extreme Pro UHS-I | 16GB RAW burst | 91.5 MB/s |
| Sony Tough UHS-II | 16GB RAW burst | 249.6 MB/s |
| Lexar 2000x UHS-II | USB 3.0 Card Reader | 185 MB/s |
| SanDisk Extreme Pro UHS-II | JPEG sequential write | 102 MB/s |
As you can see, while UHS-II is nearly 3x as fast as UHS-I in theory, real-world results are typically closer to 2x faster. But a 2x speed boost remains very significant for high volume image and video capture. Only professionals pushing the limits of UHS-I will benefit though.
UHS-I vs UHS-II – Cost Per GB Comparison
One major consideration when choosing between UHS-I and UHS-II is the cost. Here is a comparison of prices for similar capacity cards from leading manufacturers:
| Card | Capacity | Cost Per GB |
|---|---|---|
| SanDisk Extreme UHS-I | 128GB | $0.20 |
| Sony Tough UHS-II | 128GB | $0.78 |
| Lexar 633x UHS-I | 256GB | $0.31 |
| Delkin Power V90 UHS-II | 256GB | $1.05 |
| SanDisk Extreme Pro UHS-I | 512GB | $0.37 |
| Sony G Series UHS-II | 512GB | $1.25 |
Across different capacities, UHS-II cards consistently cost 2-4x more per GB than UHS-I equivalents. Unless you have specialized speed needs, UHS-I provides much better value. Keep in mind too that capacities above 256GB remain uncommon for UHS-II cards. Most models top out at 128GB.
UHS-I vs UHS-II – Lifespan Comparison
In additional to speed and cost differences, UHS-I and UHS-II cards have similar lifespans. Here are some key longevity factors:
Write Endurance
SD cards have write endurance ratings measuring how much data can be written over their lifetime. Most quality UHS-I and UHS-II cards are rated for thousands of write cycles. High-end models boast 100,000+ write cycle ratings. In practice, neither card type is likely to wear out from normal use during their 2-5 year lifespans.
Durability
Higher end UHS-I and UHS-II cards often come with durability features:
– Waterproof, temperature proof, shock proof, x-ray proof
– Vibration and impact resistance
Top cards can withstand extreme conditions like underwater photo/video, outdoor time-lapse, track testing, etc. This is more dependent on specific card models than UHS type.
Warranties
Reputable UHS-I and UHS-II cards come with 1-lifetime warranties against defects. Lexar and SanDisk offer popular “rescue data recovery” options as well in case a card gets damaged. Overall, both UHS-I and UHS-II provide reliable lifespans when purchased from major brands.
Choosing Between UHS-I and UHS-II
So when should you pick UHS-I or UHS-II? Here are some guidelines:
When to Choose UHS-I
– If you are an amateur photographer or casual video shooter
– If you don’t capture tons of large RAW or video files
– If you mostly shoot JPEGs or compressed video
– If you need up to 256GB capacity cards
– If you have a lower budget or want the best value
When to Choose UHS-II
– If you are a professional photographer or videographer
– If you shoot lots of 50+ MP RAW images or high-bit video
– If you need sustained burst mode capture without slowing down
– If you frequently fill up 64GB+ size cards when shooting
– If you do professional 4K, 6K, 8K video capture
– If budget is not an issue and you need maximum speeds
For most average users, UHS-I offers plenty of performance at a reasonable cost. But professionals who truly push the limits of their cameras and memory cards will benefit from future-proofing with UHS-II.
Conclusion
UHS-II SD cards are nearly 3x faster than UHS-I cards theoretically. But real-world speed differences are typically closer to 2x. UHS-II excels at handling large RAW/video files and sustaining burst mode shooting. But it costs substantially more than UHS-I for marginal gains in everyday use.
For most hobbyists, enthusiasts and even prosumers doing HD/4K video, UHS-I offers a great blend of speed and affordability. The extra cost of UHS-II only pays dividends for high-volume professionals capturing tons of 50MP+ RAW images or high-end 8K video. In those cases, UHS-II can save significant time in transfer speeds and post-processing workflows to justify the premium pricing. But for typical users who don’t push such extremes, UHS-I cards remain the best choice balancing performance and value.