UHS (Ultra High Speed): UHS refers to the Ultra High Speed bus interface standard used in microSD cards. It was introduced to support faster data transfer rates and improve overall performance. There are currently two UHS bus speeds defined for microSD cards:
UHS-I: This is the most common UHS standard found in microSD cards today. It supports a maximum data transfer rate of up to 104 megabytes per second (MB/s). UHS-I cards have a single row of pins on the back.
UHS-II: This standard offers even higher speeds than UHS-I. UHS-II microSD cards have two rows of pins on the back to enable faster data transfer rates. They can achieve speeds of up to 312 MB/s. However, it’s important to note that not all devices support UHS-II, and they may fall back to UHS-I speeds when used in compatible devices.
Speed Class Rating: The speed class rating indicates the minimum sustained write speed of a microSD card, which is crucial for smooth video recording and capturing burst photos. The following are the commonly used speed class ratings:
Class 2: Minimum sustained write speed of 2 MB/s.
Class 4: Minimum sustained write speed of 4 MB/s.
Class 6: Minimum sustained write speed of 6 MB/s.
Class 10: Minimum sustained write speed of 10 MB/s.
The Class 10 rating is the most relevant for modern devices, especially for capturing high-definition videos and high-resolution photos. It ensures a consistent and reliable performance during data-intensive tasks.
Video Speed Class Rating: The video speed class rating focuses specifically on video recording and is denoted by the letter “V” followed by a number. This rating system was introduced to address the increasing demands of video recording in terms of sustained write speeds. The higher the number, the faster the card’s sustained write speed.
V6: Minimum sustained write speed of 6 MB/s.
V10: Minimum sustained write speed of 10 MB/s.
V30: Minimum sustained write speed of 30 MB/s.
V60: Minimum sustained write speed of 60 MB/s.
V90: Minimum sustained write speed of 90 MB/s.
These video speed class ratings are particularly relevant for capturing high-resolution videos, such as 4K or even 8K footage, where a consistent write speed is crucial to avoid dropped frames or loss of quality.
