Do they work ? or is it directly related to the type of lense u have ?
As a cheeper alternative to another lense are they worth it - just to have some fun with ?
How much do they cost , is there a big differance in quality depending on the brand ?
Has anyone put one with an Sigma APO 70-200mm 1:2.8D , how were the results ?
What could be the biggest one that would be uesed without problems ?
As u can see i realy don't know much about lenses - i like looking through then and shooing if i thing it will look good .

I hope someone can help me - All comments will be apriciated .
thanks ....