Cheers Ross. You may find this DPR thread useful: https://www.dpreview.com/forums/thre...-post-59599687

The perfect answer for you would be the excellent recently discontinued 100-400L Mark 1, which is readily available second-hand for under $1000 .... unfortunately, it only comes in Canon mount. Possibly there are Nikon 80-400s about, but they were never all that common and (as I understand it) only the more recent version was up to the same standard. I suspect you'd pay more for one too. Tamron make a 100-400 but it doesn't seem to have a tripod ring either. After that, it's the Nikon 200-500 at around $1500, which might be getting a long way out of your range.

One thing about zooms that extend a lot (like all the 100-400s I've met): they are a bit weird to use on a tripod even with a ring because the centre of gravity changes so much. That's tolerable on a gimbal head, might be a bit of a horrorshow on a ball though.

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Out of curiosity, I just looked it up. Nope, Tamron doesn't own Kenko. Tokina doesn't own Kenko either. Kenko owns Tokina!