I'm planning to buy extension tubes for my Canon 50mm f1.8 lens. I found Kenko for about $150 but then again there are the others which are going for about $10 or less which does not mention of a brand name or anything. Any particular difference or disadvantage to using the no-name brand to the lens or camera? I find it pointless to spend lots because for sure I know that there are no optics and hence image quality should not be a problem.
The more expensive Kenko tubes have contacts that allow the lens to pass metering and aperture information to the camera, and the necessary mechanics to work the aperture, so you can use the lens as normal.
The cheap ones lack these, so you have to meter manually and your aperture will be fixed at its smallest diameter - ideally you need a lens with a manual aperture ring, which I believe is not the case with your Canon.
Canon has extension tubes as well, for almost the same price I believe. Google for "Canon EF 25II".
One thing to mention, extension tubes has no optics inside, its all air. Apart from Canon tubes, all have AF issues reported in various reviews. So, I dont think one should pay more money just for the air inside the tube. And also, be prepared to use MF if you buy anything other than Canon.
For 10 bucks, surely it's worth trying the cheap ones?
That's what I've done, and the results are quite acceptable.
I used @Paul Dixon's method to set the aperture (I'm using Canon).