Macro Photography: 8mm vs. 14mm vs. 27.5mm Extension Tube?

I am interested in doing macro photography (e.g. taking close-up pictures of bugs, flowers, coins, etc.). I have a DSLR (Nikon D40 with 55-200mm VR zoom lens). I heard that the most inexpensive way to do macro is to get an extension tube. I did some research online and found out that Nikon made 3 different extension tubes: PK-11A (8mm), PK-12 (14mm), PK-13 (27.5mm) - All 3 are pretty much the same price (~US$80). Which one should I get?? Should I get the 27.5mm one since it looks like it'll give me the most powerful close-up? Is there any "handshaking" problem with long extension tube like that? Thanks.

Macro Photography: 8mm vs. 14mm vs. 27.5mm Extension Tube?
Camera movement has to do with slow shutter speeds.



Using extension tubes is a good way to go but you may find that using a tripod is the best way to get good, steady, in focus shots. Controlling depth of field will be of more concern and will be determining the shutter speed.



The length of the extension tube will be longer with longer lenses. If you are using a 200mm focal length to get a 1:1 ratio, you will be shooting with 400mm of distance from the film plane to the end of the lens. At 55 then the distance will be 110mm from end to the focal plane. The longer the lens, the shallower the depth of field. You will just have to experiment to find which works best for you.



And yes, the 27.5mm will give you the most magnification.