What's your camera body and what's your realistic budget?
Which 300mm f/4 do you have?
Check out the Nikon 80-400mm VR thread here https://www.fredmiranda.com/forum/topic/1220559 and see if it's sharp enough for you. There are great used deals on the buy and sell that will save you hundreds over the 300mm + a TC, even when comparing used to used.
I personally have no problem with the NEW 80-400mm VR G lens, having used it for years, which I assume you are speaking about.
Dec 29, 2018 at 11:29 PM
Previous versions of ckcarr's message #14708844 « 80-400mm lens? »
