I have noticed more than a few people here use extension tubes. In the 45 years that I have had an SLR, DSLR, MILC, I have never experimented/played with tubes. As witnessed in the above post, I do enjoy macro photography (to a point - not interested in really tiny things like nematodes, amoebas or atoms).
Can you tell me - do extension tubes basically turn any lens into a macro lens? For example, say I wanted to use my Voigtlander 50mm f2 Apo-lanthar lens as a macro (rather than spring for one of their large, heavy macros, like the 65mm or 110mm), would tubes be a cheaper, lighter way to go? What sizes are recommendaed? Any downsides?
