Memory Card Speed Ratings and Burst Buffer Real-World Test

The memory card is the last link in the image pipeline, and a slow card can throttle a fast camera so thoroughly that the body’s burst rate becomes fiction. Card speed ratings are famously confusing, with several overlapping standards, and understanding what each rating actually measures is the first step to buying a card that will not become the bottleneck.The ratings measure different things, which is the root of the confusion. The class and V ratings describe sustained write speed, which is what matters for video, while the UHS speed class and the card’s quoted read and write speeds describe peak performance, which is what matters for burst shooting. A card that advertises a high read speed may still have a low sustained write speed, and that discrepancy is exactly where photographers get caught.The real-world test is the burst buffer. Fill the buffer with a high-speed burst and watch how quickly the camera clears it, and the difference between a fast card and a slow one becomes obvious in seconds.

A UHS-II or CFexpress card clears the buffer several times faster than a basic card, which means more consecutive bursts and less