What macro techniques offer an alternative to expensive optics?

I was wondering what are the alternative macro techniques people use instead of buying expensive macro optics. I know about single lens reverse macro technique; what other alternative techniques allow you to do quality macro within a budget? If yes:

1. What is it called?


2. What equipment do you need and (if any) where to buy them?


3. Does it support AF/Aperture dial?


4. What are the risks associated with it?


5. What are the disadvantages of the technique?


6. What are the Advantages in your opinion?

Feel free to add your own comments if you want, following the points.

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Answer

1. What is it called? Extension tubes


2. What equipment do you need and (if any) where to buy them? Extension tubes! (good camera stores/online will sell them)


3. Does it support AF/Aperture dial? Maybe, depends on whether the tubes maintain electrical contact


4. What are the risks associated with it? None that I can see


5. What are the disadvantages of the technique? Limited magnification increase, especially with telephotos, loss of light, possible loss of lens control.


6. What are the Advantages in your opinion? Fairly cheap, multiple length tubes can be combined to give varying magnifications.