I got the Kenko Extension tube set today. I highly recommend these over close up filters or anything other trick. There is no glass in these at all. They just put space between the back of your lens and the image sensor, which effectively enables you to focus closer than normal. Here's some samples, taken with my 50mm f/1.8. This is with just the 36mm tube attached. This is the same watch with all 3 tubes attached. The tip of a pencil. I just took these shots real quick to test out the tubes. They should give you an idea of how useful extension tubes can be. Normally, the closest focusing distance of the 50mm lens is 1.5 ft. With these I was less than 2 inches away.