A lot of people have asked me this question. The truth is, there isn't one answer because each person's camera has a different settings option for their SD slot which affects the speed at which pictures are taken and videos playback!
The fastest Secure Digital (SD) memory card is the UHS-II model. SD cards are rated at up to 312MB/s bus speed and actual transfer speeds may be slightly less than this, with some 170 tests of 160 different types conducted in several test readers showing average data rates around 250 MBps.
The next type we tested was Standard Speed Memory Card which has been used since 2005 outside North America but not including Japan yet where they still use SCMSC Type I Video Mode 1 standards despite having a higher maximum theoretical rating value as follows: 10Mbps x 16bit / 2channel = 256Kbpsx(2 channels * 24.