I hope this is the right place to post this question. I am getting one of the new XTi's and it says they are compatitable with CompactFlash (Type I & II). So I should not wory about the III's or Iv's as they would not work in the camera? Are there differences in CF cards...some faster than others etc?

Type I v. type II refers to the thickness of the cards. I suspect you will only find type I cards on the market now. (Hard drive based cards were thicker.)

I don't know what type III or type IV might be; you might post a URL if you think they are types of Compact Flash cards. But I believe you want modern type I cards from a reputable vendor. (There are stories circulating of fakes on eBay; if you buy there, use care.)

Finally, yes, there are different speeds of card. Depending on the camera it can be useful to have faster cards. See http://robgalbraith.com/bins/multi_page.asp?cid=6007 for probably more detail than you wanted to know.

Personally, last time I was shopping the prices had settled enough to make me happy to buy Sandisk Ultra IIs from a retailer I'd dealt with before.

Regards,

Giles

Giles is right. I would just add that Sandisk's model names can be confusing: Ultra II, Extreme III, and Extreme IV, for example, are all Type I cards, not types, II, or III, or IV, as you might expect.

I don't think there is a "Type III" or "Type IV" CF card at all.

-Eric

Wikipedia has some info here.

Maybe Stickbowhntr is thinking of Extreme III or Extreme IV cards... which are Type I cards.

Thanks That I beleive is what I am doing....what would be the best cards for my new Canon XTi in 2gb? Are some faster at putting image to the card when a photo is shot? I want to shoot as many bursts for action shots of daughter playing college ball( action).

Go to Rob Galbraith's data base for the CF card performance tests. Since the XTi is too new for his testing I'd guess the 30D would come pretty close to XTi's performance.

http://robgalbraith.com/bins/multi_page.asp?cid=6007-8478

The cards in blue are in the top 10%. Get at least a 2 Gig card. I'm a SanDisk fan myself, but those Ritek/Ridata cards are about half the price and up there with performance.

I've been using my XTi for a week (very pleased, and bought the 17-85 IS lens).

I have a SanDisk Ultra II 2 GB, and an Extreme III 2 GB CF card.
If you're going to shoot RAW format, I'd suggest at least the 2GB size that will hold about 100 images. If just jpeg, it'll hold about 400 to 500.

The speed difference between Ultra and Extreme only seems apparent when shooting bursts such as bracketing with RAW mode. After shooting a burst of three in RAW+L mode, it takes about 6.7 seconds for the Ultra II to finish writing to the card, and 5.2 seconds for the Extreme III to finish writing.
You can take more shots while it's writing, I don't know when the camera eventually fills up it's buffer and has to pause.

An Ultra II card will probably be fine, that's what I'd choose.

...and the other side of the equation with faster SanDisk III or IV etc. cards is how quickly the pictures xfer to you computer via a card reader.