I'm contemplating upgrading to a D300 from my present D70. My main (in fact, my only) birding lens is the AF-S Nikkor ED 300mm f.4D IF prime which I've used hand-held on the D70 for several years now, with (as far as I'm concerned) quite satisfactory results (check-out http://www.flickr.com/photos/7117259@N05/ for examples). In poor light, I generally shoot with the lens wide open at ISO 400. I'm pretty happy with the image quality at ISO400 (though a little less "graininess" would be nice) and as far as I can tell, the lens (which is a very good one) is as sharp at f.4 as stopped down. I understand from the reviews that D300 IQ at high ISO ratings is markedly improved over earlier Nikon DSLRs, such as my D70. This being so, I'm thinking I could probably get away with ISO 800 with the D300 and could thus lose a stop or 2 of aperture and still have fast enough shutter speeds for hand-holding under less than ideal lighting conditions.
So, finally (sorry for the long preamble), here's my question. In terms of image quality, with my 300mm f.4 used wide-open or stopped down a little bit, am I correct in assuming that the TC14E would give noticeably better results than the TC17E. If the answer is no, I would probably go for the 17E (for the extra reach); otherwise it would have to be the 14E. Has anyone had any experience with either of these TCs with the Nikon 300mm f.4?
Any and all opinions on any of this would be welcome.
So, finally (sorry for the long preamble), here's my question. In terms of image quality, with my 300mm f.4 used wide-open or stopped down a little bit, am I correct in assuming that the TC14E would give noticeably better results than the TC17E. If the answer is no, I would probably go for the 17E (for the extra reach); otherwise it would have to be the 14E. Has anyone had any experience with either of these TCs with the Nikon 300mm f.4?
Any and all opinions on any of this would be welcome.