http://en.wikipedia.org/wiki/Extension_tube apparently extension tubes contain nothing, no glass or any kind of mechanics. my extension tubes happens to have some glass in this. is this worthy of a wikipedia edit?
Extension tubes used for macrophotography do not contain glass elements. You might be thinking of focal extenders such as this?
First of all, Wikipedia is all information that is submitted by users/member/the public in general. As such, you can expect that some of it will in inaccurate. However, in this case, I would be inclined to agree with Wikipeida. From HERE
Yes.. they are correct. No glass in extension TUBES. For Canon shooters, the confusion is usually from Canon's terminology. Their teleconverters are called "extenders" which might lead some to believe that it is the same as an "extention" tube. Teleconverters or Canon "extenders" have glass elements. Extension tubes do not.
It is worthy of an edit but not the one you are thinking. Adding a little Quip stating that Extention tubes (not to be confused with teleconverters) and an article or stub on teleconverters, maybe.
