I currently have a Sigma 150-600mm contemporary lens which I use on a Nikon D500 camera. I am considering purchasing a Nikon 500mm F5.6 PF lens. Most of my photography is for birds where I tend to walk around a lot. I believe the Nikon lens would provide a superior image and would be more comfortable to hand hold, but would I miss the extra reach that the 600mm lens provides? And if so if I use a 1.4 teleconverter with it, is it going to degrade the image so much that I lose the perecieved benefits of an improved image?