Has anyone used the new Sigma 1.4 APO TC with the Nikkor 300/4? If so, how have the images been? I wish to keep my lenses all Nikon, but there is no 400/5.6 AF option other than third party. The Sigma TC will preserve AF and all metering funtions, according to Sigma. I would love to hear from anyone who has tried this combo. Thanks, Jim Korczak Pocono Mountains, USA