I have a Canon 40D. I have always used Sandisk Extreme III 4 GB Compact Flash cards that say 30 MB/s and currently have 3 of them. I love them and have never had a problem. Now I want to buy 3 more but I notice the 4 GB cards now have 40 MB/s on them. Are those still ok to use in my 40D?

Most of the current compact flash (CF) cards use UDMA technology to speed transfers. The Canon 40D is not UDMA enabled, so many of the latest Cf cards with UDMA are 'slower' than some of the older non-UDMA cards. While the cards may be slower in the camera, if you have a UDMA card reader, you may still benefit from using that to transfer the files into your computer.

Rob Galbraith has deleted the links from his older camera and card tests, including the 40D card tests, but the results are still available via the Internet Archives "Wayback" project:

http://web.archive.org/web/200904131...?cid=6007-9257

Transcend 133x and 266x CompactFlash appear to be UDMA mode 4 cards that still work well with the 40D and should provide good speed as well as good value, for instance.

http://www.newegg.com/Product/Produc...d+133x&x=0&y=0

I have used most brands out there early on in my switch from film to digital....and have spent the last several years using only Transcend cards...I have never had one to corrupt or fail on me... ... ... and I know it is not a matter of if...but when...at this time I have a total of 16 cards ranging from 80X to 600x and all working like champs ... ... ... and I also have really great card recovery programs on stand by at all times......

Thank you both for your thoughts on this. This is why I enjoy this forum so much, getting ideas from folks who have been doing this a lot longer than I have!

I use SanDisk only now. Bought 3 Lexar 3 years ago and 2 out of 3 failed within 3 months of purchase.

I use various Sandisk, purchased at different times (Ulltra, Ultra II, Extreme). 2-4-8 GB . All work well. I had one Lexar unit fail, and their customer service did nothing.
Stan