may be my question will look like not a professional at all: what the difference between Class 6 and regular ultra?
I've used both Sandisk Class 10 (Ultra) and their and other's Class 6 and the difference is measurable, but not significant (16 vs 20 MB/sec capable~~only using about 10-12 Mb/sec anyway). Never had a Sandisk go bad, competitors (one beginning with "K" and another "L" had to be returned for exchange)~~both did so, but never had to send Sandisk memory back! Better security in not losing data, if it never goes bad!!!!!! Class 6 is fine for my Canon S100 (almost DSLR) camera, both pictures/video capture! NEVER get/use std SD base memory speed for newer cameras.