Both U1 and U3 are graded for reading and writing speed of TF or micro SD cards, and the two are mainly different in reading and writing speed and compatibility. In terms of speed, U1 can reach a write speed of 10MB/s, while U3 can reach a write speed of at least 30MB/s; in terms of compatibility, the U1 device into the U3 card can only support the highest U1 speed. The following is a detailed introduction:
Speed: U1 means to reach UHS Speed Class 1, UHS refers to Ultra High Speed, the English abbreviation for ultra-high speed, U1 speed is a minimum of 10MB/s writing speed, U3 is UHS Speed Class 3, the lowest writing speed The input speed is 90MB/s;
Compatibility: If the device only supports the writing speed of the highest U1 level card, if the card inserted in U3 can only meet the speed of U1, if the device supports the speed of U3, the card inserted in U1 can meet the full speed of writing Entry needs.
In addition, if you want to shoot 4K high-resolution video, you need to ensure that you use a TF card with the lowest U3 level to satisfy the video data writing.