How to Pick the Right SD Card for your Camera
Picking the Right SD Memory Card for your Camera by mikemuonline
For most new cameras, any SD card that you get that is 64GB and above will work just fine. Why 64GB cards? Well its close to the sweet spot in pricing, and speed performance. The key differences you want to watch for are the durability, and write speed. The read speed will typically meet or exceet the write speed specification. If it doesn't show the write speed on the packaging then its likely not the best - so watch out if your Video mode requires a certain bit-rate.
If you have an older camera (more than a few years old), you may have to get SDHC cards or below - stick to 8GB SD Cards. Pay attention to whether the camera supports SDHC or SDXC cards with the XC ones being the newer, faster, higher capacity capable specification.
For 4K video, on the higher spec cameras you will want to look into something like the following:
And even those are not high enough for the highest 100MBps rating required to unlock the RX series 100 MBps video.
Some newer cameras designed to be pocketable use physically smaller cards called micro-sd cards. They're about the size of my pinky's fingernail and are compatible with cameras that use SD cards if you use a MicroSD adapter.
Fastest cards right now: