Memory card speeds are important to the overall performance of your camera. Here are three things you should consider: Transfer speed: how quickly data (images or video) can be downloaded from the card. Faster transfer speeds require less time to import photos or ingest video to your computer. Write speed: how well a card performs in a camera. Most camera manufacturers do not disclose an exact specification. Instead, they simply specify the speed class rating that the camera requires. Speed class: professional-level cameras typically require the newer Ultra High Speed (UHS or UHS-II) categories described as U1 (10MB per second) or U3 (30MB per second). It’s best to match the speed of the memory card to the requirements of the camera.