Originally Posted by oldmandon
Shouldn't the 8GB card be faster than the 4GB or am I missing something?
The way SDHC cards are marked, the 4GB and 8GB figures are the capacities
-- the amount of data the card can hold. To help visualize this, just assume that "4GB" stands for "4-gallon bucket" and "8GB" stands for "8-gallon bucket."
What Brian's talking about are "class" ratings, which are speed
ratings that, basically, tell you "how fast you can fill the bucket." A Class 6 card is supposed to have a minimum sustained transfer rate
of 6 megabytes per second, which makes it "faster" than a Class 4 (4 mb/sec) or Class 2 (2 mb/sec) card.
However, these are minimum rates, so it's possible for one Class 6 card to be faster than another. Also, since they're based on sustained
transfer, they're mostly relevant to video recording, where the camera is continuously sending a basically constant volume of data to the card. Still cameras send their data in bursts, so a card with a higher sustained
rate but a lower maximum
rate may perform more slowly than one that's vice-versa.