These lenses are usually used for sports and wildlife photography but my application is a little different. I am interested in doing ultra high resolution "close up" images of small plants in the wild. I use a Nikon D800e. Right now I am using a 28-300 mm Nikkor walkabout. I find that I cannot get full closeups due to the size of the subject and the intervening terrain which makes it difficult if not impossible to approach the subject more closely.
I am looking at the newly released Sigma 150-600mm FX and the Sigma 50-500mm ($900) and the new Nikon 200-500mm ($1400). The word out there is that the Nikon has better image quality and a better IS system. I am wondering if it is worth the extra $500 bucks?
Last question: has anybody done any testing on the addition of top quality 1.4 teleconverter to these lenses?