There's a wide variety of SD cards available on the market, with the most common being the standard SD card and the microSD card. They're mostly used with digital cameras as well as with a few less common devices, like multimedia players.
But even within the most common SD card formats, there's a lot of variety, and it's important to know about the differences in order to make the best choice when you're buying an SD card.
What's the difference between SD, SDHC, SDXC, and SDUC?
1. Storage capacity
SD (SDSC, standard capacity SD card): maximum storage capacity is 2GB. This is an early SD card standard. With the development of technology, its capacity limit gradually became insufficient.
SDHC (high capacity SD card): storage capacity exceeds 2GB but does not exceed 32GB. This standard met the demand for larger capacity at the time.
SDXC (extended capacity SD card): storage capacity exceeds 32GB but does not exceed 2TB. The SDXC standard further improves storage capacity and meets the storage needs of data such as high-definition videos and large amounts of photos.
SDUC (ultra-high capacity SD card): storage capacity exceeds 2TB but does not exceed 128TB. This is the latest extension of the current SD card standard, mainly used to meet the demand for ultra-large capacity storage, such as 4K/8K video shooting.
2. File system format
SDSC: only supports FAT12, FAT16 and FAT16B file formats.
SDHC: almost all use the FAT32 file system, which performs well in read and write compatibility.
SDXC/HC: Most versions use the exFAT file format, which is designed specifically for NAND flash devices and can support larger storage capacity and more efficient data management. However, there may be some minor issues with multi-system compatibility.
SDUC: Since SDUC cards are still very new, the file system format they support may still be evolving, but more advanced file systems are expected to be adopted to support their large storage capacity.
3. Speed Class
All SD cards use different speed grades to describe their performance, which are usually defined based on peak bus throughput (i.e. the maximum number of bytes that can be transferred per second). For example, Class 2 means a read and write speed of 2 MB/s, Class 10 means a read and write speed of 10 MB/s, and so on.
For application scenarios that require higher speeds, such as high-definition video recording and playback, SD cards also support ultra-high-speed (UHS) classifications, such as U1 and U3. U3 has a throughput three times higher than Class 10, reaching 30 MB per second, which is enough to shoot 4K video at a high frame rate.
The SD Association also provides video speed grades (such as V10, V30, V60, etc.) to better communicate the suitability of SD cards for video recording.
4. Compatibility
Digital devices that support SDXC cards are generally also compatible with SD and SDHC cards, but not all devices support SDXC or SDUC cards.
SDUC cards may have limited compatibility due to their large storage capacity and the new technologies they may use.
What's the difference between UHS-I, UHS-II, UHS-III, and SD Express?
"UHS" is the abbreviation of "Ultra-High Speed". UHS memory cards generally have faster reading and writing speeds. This standard is formulated by the "SD Card Association", a non-profit organization, and there are several versions:
。UHS-I (the first generation of ultra-high speed) was released in 2010, and the theoretical transmission speed can reach a maximum of 104 MB/s. It's suitable for daily use, such as taking photos and recording videos.
。UHS-II SD cards can reach 312 MB/s which is suitable for taking high-definition video and high-definition pictures in 4K.
。The UHS-III specification was released in early 2017, doubling the previous UHS-II rate and achieving unprecedented transfer speeds of up to 624 MB/s. It's suitable for devices that need really fast data transfer, for example, professional cameras used to record 8K, 4K, and 360-degree video.
。SD Express offers the fastest data transfer rates of up to 3940 MB/s using the PCIe Gen.4 interface and NVMe application protocol. It supports dual-channel reading, and the interface speed is close to 4 GB/s. Unfortunately, there aren't any devices that have adopted this standard yet, but in the future, it should mean we can enjoy much faster data transfer speeds.
It's important to make sure that the card reader you're buying is compatible with your memory cards. In addition, you should choose your memory card based on your personal needs. If it's for daily use, a microSD card or SD card with UHS-I will get the job done. If you need something with higher performance, then a UHS-II SD card would be a better choice.
Another thing to consider is that since 2016, Apple has switched to USB-C ports on its laptops, and has stopped including a card reader as standard. This means that MacBook users will need to buy an adapter or a USB-C to SD card reader.
First up is our 2-in-1 SD 3.0 card reader which supports both microSD and SD cards, and can reach speeds of up to 104 MB/s.
The second is the 2-in-1 SD 4.0 card reader which also supports both microSD and SD cards but has a much higher top speed of 312 MB/s.
