Question Re: card speeds.

[Jonny]

Guys:

With Sandisk just producing the Extreme IV i was looking at card speeds on Rob Galbraith's site when i saw something that i never really noticed before. I know there will be a simple explanation somewhere.

The Sandisk extreme 4 has a read/write speed of 40 MB/Sec but on the RG database it shows about 7 MB/sec write speed in the camera. Why?
My guess is that the camera cannot write to the card at it's full potential but if that was the case why can't it write at 7 MB/sec to a cheaper card that has a max of 10MB/sec.

Kinda confused.....help me out.

[DavidW]

There are multiple bottlenecks in a card writing operation. The main one is, as you identify, that there's a limit as to how fast the camera's circuitry is able to provide data to the card when writing. However, there are other factors in play, influenced by the card design, such as how fast the card responds to each write command.

A faster card will probably take less time to service each write command, and will therefore write faster than a slower card in the same camera.



David

[deadpass]

I think the max bus speed for canon cameras is around 7mb/s