I was never a fan of extenders on camera and lens after wasting money on Canon Extenders and suffering with image quality. But the Sony 1.4is just amazing with the focus speed and image quality being just as good at f9.
Today was nothing special and I went out quickly to test the 200with the ext fitted. The ducks were flying and it was very windy. Anyway look at the results from this carking combination.
Even birds in-flight is amazing and I had no problems with tracking as this image of two mallards flying fast left to right.