The largest number on the face of the card represents its capacity as measured in gigabytes, which will impact how many still photo frames or video minutes a card will hold. If you are just shooting JPEGS and occasional video, you can get away with a memory card that doesn’t hold much storage space. But if you plan to shoot data-intensive RAW images, full HD, or even 4K Ultra HD video, then capacity and write speeds become more critical. In simplest terms, the more you ask of your camera, the more capacity and space you will need. Action photography, such as stopping a fly-rod cast in mid-motion, or capturing a bird in flight, often requires shooting in memory-hogging burst mode. Shooting flies in a vise or taking grip-and-grin photos does not.