Cameras & Camcorders

[#1]

Hi, how do I compare the speed of SD and CF cards, some say it is 133X or something, some say ultra or extreme I, II or something, some even don't have any information? Thanks!

[#2]

For every "x" it means 150KB/s

* 4x: 600 KB/s
* 16x: 2.4 MB/s
* 40x: 6.0 MB/s
* 66x: 10MB/s
* 133x: 20MB/s

You may also see classes, which to me are a bit more confusing. A class 2 card is generally around 2MB/s, class 4 gives you 4 or 5MB/s, and a class 6 card 20MB/s, but I've seen exceptions. If anyone can clarify classes that'd be great.

[#3]

Although class 6 cards can transfer 20mb/s, people generally forget what these classes mean:
Class x means the card has a minimum sustained transfer rate of the class number, meaning the card will never go slower than that. If you have a class 6 card, the card is guaranteed to never transfer slower than 6mb/s.

[#4]

Ahah, that's why I saw a class 6 at 6MB/s and another at 20MB/s.

[#5]

Does this mean that those cards can transfer an arbitrary amount of data at a continuous rate to or from the card, at that rate?  What about its wear-leveling and flash write delays?

[#6]

There is so much marketing confusion out there.  Here's a link that may of interest of someone who took the time to speed each card.

http://www.robgalbraith.com/bins/camera_multi_page.asp?cid=6007-9254