I was curious where I might find some good info on stop loss and image degridation from the use of teleconverters. I am waffling on which lens to put my savings account crosshairs on and a faster zoom lens in the 200max focal lenth is becoming appealing (70-200 2.8 VR). I am lured by the reach of the 80-400 4-5.6VR but I already have a 70-300 4-5.6 that is very often too slow and think what I may need is speed not reach. Questions I am looking to answer How many stops lost on a 2x converter? What other negitive things happen with 2x? Vigneting? etc. Does VR still work? Focus Speed? Can you tell how deeply this disease is working it's way into my system. Best illness Ive ever had!