When it come to photographing small objects you a few choices. you can buy a Macro lens or you can pick up some extension tubes. The macro lens route will give you a better image quality in the end but will also take a bigger chunk out of your bank account. If you're like me and you don't do a lot of Macro work then a good option might be the tubes.
What the tubes do is decrease the minimum focusing distance of your lens. Each lens has a limit to how close it can be to a subject before it can't focus on it any more. the For the images above I used my 50mm f/1.8 and all three extension tubes. The closest I could get without the tubes was about 14 inches away. With the tubes the flowers were almost touching the front of the lens (1 or 2 inches away). You don't have to use a 50mm like mine. A lot of people use a longer lens so they can be a little farther away so their lens/camera will not cast a shadow on their subject. I tried it with my 70-200mm f/2.8 but liked the look I got from my 50mm.
A few things you have to know before you start using extension tubes are as follows:
- Use a tripod! When you're really close the slightest movement is magnified just as much as your subject is
- Your depth of field is a lot shallower then normal so close down you aperture more to get more depth of "focus" in your image.