After considerable thought and research, I believe my auto focus problems with the 200-500 lens may be caused by firmware that requires updating on this lens. I have had occasional difficulties with focus with subjects where there is low contrast but also with brightly lit colorful subjects. Coupled with my challenge with birds in flight my desire to find a solution compelled me to search some more. I have finally found that my lens is one of those that requires a firmware update. Maybe the Nikon service center in Toronto will open soon.
Marsha
Lethbridge,Alberta
MY WEBSITE Etched Images