Help me choice Extension Tubes.

I want to buy Extension Tube. I don't know which type better between Canon Extension Tube EF 12 II or Canon Extension Tube EF 25 II? Please show for me differents? And how about Kenko brand? It have 36mm tupe. It's good?

Most people will tell you to go with the Kenko tube set because it's cheaper. An extension tube has no glass so there's no effect as there is with cheap filters. Both the Canon and Kenko have contacts to allow for autofocus although that's almost pointless when you're so close to the subject.

Another benefit for the Kenko tubes is you can get them in the set of 3 which is a great deal. As the post above states...there's really not a benefit to Canon "air" over Kenko "air. The build quality is essentially the same. I went with the Kenko 3 tube set.

- Chris

The difference between the Canon 12 mm tube and the Canon 25 mm tube is how close you'll be able to focus with any given lens. With a 25 mm tube on a 50 mm lens, your lens will start focusing at 1/2 life size; with a 12 mm tube on the same 50 mm lens, you'll get about 1/4 life size as a starting distance, and won't be able to focus as close as you will with a 25 mm tube at the nearest end, either. If you get the Kenko set of 3 you'll have both these options and more, for about what a single Canon ring will cost. The biggest difference, unless I've missed a Kenko design change, is that Canon's Type II close-up lenses will connect to Canon's EF-S lenses as well as to the normal EF mount. I believe people have removed a baffle from the Kenko tubes to be able to mount EF-S lenses, but it's something to bear in mind if you have only EF-S lenses.

I have 18-55 is and 50mm f1.8, and to use both of them, Canon extension tube is the best choice?

Checking Adorama's site the Kenkos may fit an EF-S lens, but may not AF with all of them. If you want to use the tubes on your 18-55, yes, you should probably get the Canon ones. But I'd suggest getting the Kenko set and just using it on the 50 mm f/1.8. The full set of 3 tubes will get you past life-size (about 1.25x life size, in fact) on that, with better working distance (how far your lens is from your subject) than the 18-55 and a single 12 mm or 25 mm tube would be able to give you.

Thanks Jon! Someone said "Kenko Auto Extension Tube Set DG (12, 20 & 36mm Tubes)" can use with with my 17-70 Sigma lens and my 55-250 canon EF-S lens.

May or may not work well with the 55-250; I don't know. I don't have any EF-S lenses since I only have one body that would accept them.

If it's a choice between canon 12 and 25 , go for the 12 , You can add another 12 later if you want 25 .
The newer kenko's have some electronics' built in . Either one - canon or kenko - You will lose about 10%+ when / if you sell .
Kenkos are cheaper so easier to sell . I just picked up a macro rail w/ bellows off ebay - so watch there . The rail starts at about 35 mm . There's also lens reversing adapters [about 10 bucks - ebay] lens couplers and screw on magnifiers - best [to me] are the canon 250 D and 500 D .
Good luck .

And one more question: If use Extension tube, you must be get AF by manual or automatic?

Depends on luck , lens and distance .
That said - you will use manual unless you won the lottery .

This thread is a bit old now, but I thought I'd add a comment in case anyone is searching for info on this topic.

I just bought the kenko 3 tube set and it clearly indicates on the box that they are EF/EF-S compatible. I have tried them with several EF and several EF-S lenses and they work perfectly fine with all of them.

Also, the build quality seems to be very good in my opinion. They are rock solid when connected to my 40D. Even with all 3 tubes connected in series, I feel no wiggle or looseness of any kind. They fit very tightly to all my lenses.

Oh, and the Kenko air that came with them is great. I'm just starting to explore macro photography and they are a very cheap way to get started.

and your DOF is so narrow you'll manually focus all the time anyway so don't worry about autofocus.