I have been looking into teleconverters and I noticed that there are 2 different types. one that screws onto the tip of the lens and one that goes between the lens and the camera body. Is there a difference between these 2? I have a cheap one that goes on the front of the lens, it is not any help at all. It makes the pic very distorted. It's so cheap it doesn't even have what size it is or anything on it. Just made in Japan. I have read that I should stick to name brands when buying one. But what is a good brand for these? I'm looking for a 2x with a 46mm screw for a Minolta AF lens.Any suggestions?