I'm still learning how to use this Nikon 400mm Ai-S lens. It's an older, non-CPU lens with manual focus. I used a Nikon 1.4TC with it for these shots yesterday morning. What's a challenge in these long lenses is getting the focus right with such a narrow depth of field. The eye of the bird is key. If that's not in focus, the shot is ruined. This is the best one I got yesterday morning.