Can someone please exlain the math behind macro ratios? For example, I have a Vivitar 100mm macro lens that shoots 1:2 without the diopter on the front. Now lets say instead of the diopter I use a 1.4x telecoverter. What is the lens actually shooting at now? Then lets say I have a 21mm extension tube coupled with the 1.4x teleconverter, where am I at now? If someone could please explain the math and give some examples that would be awesome!! Thanks!