Have you thought about getting a reflex lens? They are really inexpensive (even new ones) and you can learn a great deal from using them.

I have had 600mm (f/4 and f/5.6) lenses and I can not justify the expense and the back breaking weight, [I use my photography as a business and there is no way I could make a profit on super long lenses] but I do have a Nikkor 500mm f/8 that is pretty good even if rather limited with respect to f/stop. I even use it with a TC-14B. And you can avoid the donut shaped bokeh in many cases if you are careful.

But you can learn a lot using one. And you don't have to tell the pixel peepers what lens you used ...

David Jenrette

Doesn't work with a TC - sharpness is pretty bad at 300mm, it is F5.6 at 300, and to get usable sharpness you need to stop down to F8, so effectively you will be shooting at F11 and the quality will be pretty bad.

If you are set on using a TC, the 300 F2.8 will be a first choice, and if you use an F4 version, then at least your image quality will still be excellent. The 28-300 is an all-around superzoom that does nothing exceptional - ok for snapshots, but there are better lenses with less reach that are really pretty good. I have used 3 different copies, a friend's and two out of Nikon's NPS program - I am not a fan - though I had high hopes that it would be at least as good as my 18-200 was on my cropped cameras. It isn't even close. And it you are looking for quality at 300mm, then you should be looking elsewhere. If you don't mind buying used and third party, I am sure you can find a Sigma 100-300 F4, which does satisfy my quality standard, and can be found in great shape for $500-$600. I paid $550 for mine a year ago. Images taken with it rival my 600 F4, except for the bokeh, which can be a little "nervous" sometimes.

The first three attached images were all taken with the Sigma 100-300 and a D800 and cropped considerably.

The last one was with a 600mm F4

As you can see, the image quality is comparable.

You have to be careful putting a TC on zooms. The glass on the lens and TC will hit and break if you zoom in. I have a Bowwer I use on it once in a while that does pretty good. But just the lens alone works great by it's self. I never try to shoot a mile away.:):) If you look at my post about the Blue Heron, he was about 75-100 yards away from me. And the shots I posted were cropped as tight as I could get them.:):) Just click on my user name and hit the list button. Most of what I put on the site is with the 28-300.
Erv