I took my 400mm with my new Tamron 1.4TC to the local beach to try it out for the first time. I used auto focus and the focus was a little slower than without the 1.4TC and some times it would hunt before focus. Over all I'm pleased with the combo as it now gives me a 560mm lens. I had never seen this type of heron before and had to look it up in the bird book to identify it.