Just got my 5D, I am so excited to shoot some footage. Any thoughts on CF cards? I am not sure what I actually need. What speed in needed? Is Transcend any better or any worse than the others. It is priced much better. Anyway with all the spending on toys, I don't want to cheap out on the cards, but if one is as good as the other, the why spend more.
The thing you need to understand is the actual data rate of the card and what the data rates of the 5D actually are. Card manufactures chose to use 150 KB/sec as the base value for CF cards. So when a card is rated say at 133x that really means 133 x 150 KB/sec which translates to 19950 KB/sec or roughly 20MB a second. A new fast 533x card for example can record at up to (rounded up) 80 MB/sec. The Canon cameras depending on frame rate and size you shoot at have a data rate of between 3-6MB/sec
So the slower cards will work just fine just make sure they're UDMA rated. Also just be aware the the downside of the slower card is slower transfer off the card to your backup device or computer.
Personally I save the faster cards for doing burst still shooting
I did have issues with a Kingston pro x1333 card, my Canon 7D went into buffer over run and closed the camera down, it did this three times in a row, only allowing 3 seconds of shooting and then closing down the camera. The card was 50% full, so now I'm looking towards Sandisk Extreme.