SD cards have various symbols printed on them that indicate different features and specifications. These symbols help users understand the capabilities of the SD card and ensure compatibility with devices. Some of the common symbols found on SD cards include:
Speed Class Symbols
Speed class symbols indicate the minimum write speed of the SD card. Higher speed class cards have faster write speeds and are better suited for recording high-resolution videos and images. Some common speed classes are:
- Class 2 – Minimum write speed of 2 MB/s
- Class 4 – Minimum write speed of 4 MB/s
- Class 6 – Minimum write speed of 6 MB/s
- Class 10 – Minimum write speed of 10 MB/s
- UHS Speed Class 1 – Minimum write speed of 10 MB/s
- UHS Speed Class 3 – Minimum write speed of 30 MB/s
A higher speed class symbol means the card can support faster data recording and transfers. Most digital cameras and camcorders require at least a class 10 card for HD video recording.
UHS Bus Symbols
UHS (Ultra High Speed) bus symbols indicate the SD card’s supported bus interface speed. It determines the card’s capability to transfer data quickly from the card to the device. Common UHS bus interfaces are:
- UHS-I – 104 MB/s bus speed
- UHS-II – 312 MB/s bus speed
- UHS-III – 624 MB/s bus speed
Cards with a higher UHS bus rating offer faster transfer speeds when reading from and writing to the card. UHS-II and UHS-III cards allow quick transfer of 4K and 8K video recordings.
Capacity Symbols
The card capacity is printed in GB (gigabytes) or TB (terabytes). This indicates how much data the SD card can hold. Higher capacity cards can store more photos, videos, audio files, and other data.
- 4GB
- 8GB
- 16GB
- 32GB
- 64GB
- 128GB
- 256GB
- 512GB
- 1TB
The capacity required depends on your storage needs. A 16GB card may be sufficient if you just need to store some photos. However, 4K video recording will quickly fill up cards and require 64GB or higher capacity.
Card Format Symbols
This symbol indicates which devices and equipment the SD card is compatible with. The common formats are:
- SDHC – SD High Capacity, compatible with SDHC and SDXC devices
- SDXC – SD Extended Capacity, compatible with SDXC devices only
SDHC cards have storage capacity between 4GB to 32GB, while SDXC cards range from 64GB and above. The right card format must be used with supported devices.
Wireless Symbols
Wireless SD cards have symbols indicating connectivity options that allow data transfer over Wi-Fi networks. This enables sharing of data between devices like cameras, smartphones, and computers without physically moving the card.
- Wifi symbol – Can connect via Wi-Fi to upload content
- Wifi Direct symbol – Can directly connect with Wi-Fi enabled devices
Wireless cards need to be coupled with an app on the device to transfer data. This gives more flexibility when sharing videos and photos from a camera.
Video Speed Class Symbols
Video Speed Class (VSC) symbols indicate the minimum write speed for recording video to the card. Higher VSC ratings support recording of high resolution, high bitrate video formats.
- V6 – Minimum 6MB/s write speed
- V10 – Minimum 10MB/s write speed
- V30 – Minimum 30MB/s write speed
- V60 – Minimum 60MB/s write speed
- V90 – Minimum 90MB/s write speed
A V30 card is typically required for 4K video recording. V60 or V90 cards allow recording of high quality 8K or 360-degree VR videos.
A1/A2 Symbols
The A1 and A2 symbols indicate the card’s suitability for apps. The A1 prefix specifies read/write speeds of at least 10MB/s, while A2 ensures random read speeds of 4000 IOPS and write speeds of 2000 IOPS for smooth app performance.
Resizable BAR Support
The Resizable BAR symbol indicates that the SD card is compatible with the ReBAR technology that allows full access to the card’s memory buffer for improved performance.
NVMe Symbol
NVMe stands for Non-Volatile Memory express. Cards with this symbol use the NVMe protocol to provide faster read/write speeds compared to UHS cards. NVMe cards offer sequential read speeds over 2000MB/s.
V guaranteed Symbol
The ‘V guaranteed’ symbol indicates the card maintains the labelled minimum sustained write speed rating throughout its lifetime. This guarantees consistent video recording performance even after long-term usage.
Class Symbols for Apps
App performance Class symbols indicate the card’s performance for running apps and gaming on smartphones and tablets:
- App Performance Class 1 (A1) – Faster app loading and performance compared to standard cards
- App Performance Class 2 (A2) – Even faster app loading and caching performance compared to A1
Cards with A1 or A2 rating provide improved user experience when running intensive apps or games on mobile devices.
Speed Class Symbols for Cinema and 360° Video
Newer speed class standards cater to very high video recording bitrates like cinema quality or 360° VR videos:
- UHS Video Speed Class 60 (V60) – Minimum write speed of 60MB/s for 8K video recording
- UHS Video Speed Class 90 (V90) – Minimum write speed of 90MB/s for 8K or 360° video at high frame rates
V60 and V90 guarantee sufficient performance for smooth high resolution or 360° video capture.
Video Speed Class for 8K Video
For recording highly detailed 8K video, the V90 standard indicates a minimum write speed of 90MB/s. This ensures smooth and consistent writing of very high amounts of visual data per second to the card when capturing 8K footage.
The Difference between V30, V60, and V90
The Video Speed Class standards V30, V60, and V90 denote increasing minimum write speeds:
- V30 – Minimum sustained write speed of 30MB/s
- V60 – Minimum sustained write speed of 60MB/s
- V90 – Minimum sustained write speed of 90MB/s
V30 is suitable for 4K video recording. V60 can handle up to 8K video recording at standard frame rates. V90 is ideal for very high resolution like 8K at high frame rates or 360° VR videos that require very fast constant writes.
SDSC vs SDHC vs SDXC
SD cards come in three interface standards:
- SDSC – SD Standard Capacity cards up to 2GB
- SDHC – SD High Capacity cards from 4GB to 32GB
- SDXC – SD Extended Capacity cards from 64GB and above
Devices and card readers that only support SDSC will not be compatible with higher capacity SDHC and SDXC cards. Check your device supports SDHC or SDXC before buying higher capacity cards.
Does the brand or color of the SD card matter?
The brand, color, or design of the SD card typically does not matter in terms of performance or compatibility. The technical specifications like speed class, capacity, and interface standard are what determine the card’s capabilities and suitability for your device. Some brands may have faster rated speeds or longer warranties. But any reputable brand that meets the required specifications should work reliably. The color or look of the card is generally for visual identification only.
Why do some SD cards have locks on the side?
Some SD cards have a small physical switch or tab on the side that can be slid up to lock or down to unlock. This write-protect lock switch prevents any new data being written to the card when it is in the locked position. It helps avoid accidental deletion or overwriting of data on the card.
What is C10 vs U3 for SD cards?
C10 and U3 are both speed ratings for SD cards:
- C10 – Guaranteed minimum sustained write speed of 10MB/s
- U3 – Sustained minimum write speed of 30MB/s
U3 is 3 times faster than C10, making it better for 4K video recording. C10 is sufficient for Full HD video recording. The higher the MB/s, the more data can consistently be written to the card per second when recording high resolution videos.
What are the best uses for each SD card speed class?
Here are the recommended uses for different SD card speed classes:
| Speed Class | Recommended Uses |
|---|---|
| Class 2 | Basic photo shooting |
| Class 4 | SD video recording |
| Class 10 | Full HD video recording |
| UHS Speed Class 1 | Full HD video recording |
| UHS Speed Class 3 | 4K video recording |
| V30 | 4K and cinema quality video |
| V60/V90 | 8K, 360° VR, and high frame rate video |
Using the appropriate speed class card ensures your recording device can smoothly write the very high data rates required for high resolution, high framerate, or special effect videos.
Do microSD cards have the same meanings for their symbols?
Yes, microSD cards use the exact same speed class, capacity, and compatiblity symbols as full-size SD cards. microSD cards are simply a smaller physical form factor, but provide equivalent capabilities as their larger SD card counterparts if they have the same specifications and symbols.
Conclusion
SD card symbols help summarize the card’s intended performance, video recording abilities, capacity, and device compatibility at a glance. Matching these specifications closely to your use case and devices ensures you get a card that works reliably for features like HD video recording or fast action photography. Understanding what the main SD card symbols mean helps you pick the right card for your camera, smartphone, drone or other device.