I am new to the 5D, and Canon for that matter. My question is about the Canon 2 x Extender. I looked at one on Ebay (New) and the sellers remarks indicated that it would only work with a lens that was 2,8 or faster. I looked at the information on Canons web site and saw no mention of this restriction.
Can anyone that has used this extender comment on either how you liked it as wel as this restriction mentioned on the Ebay listing.
Thanks in advance for any input.

With the Canon 2X extender you loose 2 full stops of light so if it's used on a F2.8 lens the light coming into the camera will be like it's got a F5.6 lens on it. On some cameras (but probably not the 5DMkII) the auto focus will then struggle (and indeed your eyes may struggle) with much less light available in the viewfinder etc.

I had the Canon 2X on extended loan (used it with the 70-200 F2.8 IS and 70-200 F4 IS) and in the end I bought the Canon 1.4X extender since this looses only 1 stop of light and shows much less image resolution/degradation (as seen with my 7D). This was was especially noticeable in stills, much less in video. The best stills photography websites will give you more information on these converters but hope this helps.

fredmiranda.com: Specialized in Canon - Nikon SLR Cameras, Forum, Photoshop Plugins, Actions, Reviews, Hosting and Digital Darkroom (http://www.fredmiranda.com) is a good site for reviews of Canon and Nikon lenses.

The reviews of the tele-converters can be found in:

Reviews, then
Digital Photo Acccessories, then
35 mm accessories.

There are reviews of the "II" editions of both the 1.4 and the 2.0. The 1.4 II is more highly rated.

Richard and Andy,
Thank you for your quick response to my questions. The info is very helpful.

Tom

Tom, there is a good summary review of the Canon 2X extender (and indeed the 1.4X and many other lens reviews on this site I link to below). It also mentions that a review for the new Canon 1.4X III and 2X III versions are planned - see the huge long list of reviews at the bottom of each page.

I have no idea if this new 2X III version will correct some of the things that I did not like with the 2X II that I had on loan but someone might know - but it will still cut 2 stops of light. I'm VERY happy with my 1.4X II but note that I have a 7D which has longer reach anyway than the 5DMkII (for obvious reasons):

Canon EF 2x II Extender Review (http://www.the-digital-picture.com/Reviews/Canon-Extender-EF-2x-II-Teleconverter-Review.aspx)

Canon official release on 1.4X III and 2x III extenders below which mentions improved optics, coatings, reduced flare etc:

Canon Europe - Extend the reach of your telephoto lens with Canon?s Extender EF 1.4x III and Extender EF 2x III (http://www.canon-europe.com/About_Us/Press_Centre/Press_Releases/Consumer_News/Cameras_Accessories/Extender_EF_1.4x_III_and_Extender_EF_2x_III_Press_Release.aspx)

Use the Canon 2x extender with a 70-200 f4 with IS on Canon 5DMll with video, locked down on tripod. No issues using outside. Perfect for video.

I use mine with a 70-200 2.8 and it's fine.
My mate uses his with the 70-200 F4 and it's also good.

Both on 5D2s

Steve & Wayne, are your extenders the EF 2X II or the newer III models?

the older model.

I have the 2x II. All 2x extenders lose at least two stops of light due to physics. The f/2.8 thing has to do with autofocus. If you have a slower lens, apparently, autofocus won't work. One thing for sure, my 200/2.8L II focuses much faster and more reliably on its own than with the extender. That said, it was a cheap way to get more reach.

Thanks everyone for the input. It has been very helpful.
At this point I think I will sit tight and wait for a review of the new versions. Until then, I'll spend my time getting use to the camera and deciding on lenses.