Tamron SP AF 1.4x Pro Teleconverter for Nikon Mount Lenses Review

I have been shopping for a fast (large apperature=small number) longer lens than a nikon 80-200mm f/2.8D that I use. I have a longer sigma lens, but it has a slower apperature (f/5.6-6.3). Fast lenses are quite expensive, so I looked at other approaches & arrived at teleconverters to extend the length of my 80-200mm lens. I read a lot online (the above review was not helpful, no offense) prior to deciding to give this tamron SP pro 1.4X TC a trial.
First off, I found it used at a reputable on-line camera outlet for about $50 less than the $180-$190 retail price as of late 2008.
Basically, it works OK -- Using a D-300, I've tried it with the 80-200mm f/2.8 (which turns it into roughly a 112-300mm f/4 lens) and the autofocus is still very quick. The quality of hte photo appears about normal (a steady tripod would probably be very helpful; i was using a monopod).
Though not recommended for lenses "slower" (larger number) than f/2.8, I tried w/ a Nikon 70-300mm, f/4.5-5.6, AF-S VR lens and was pleasantly surprised that it took decent photos --it focused OK, the VR seemed to remain operational, and the quality was OK-- as long as there was sufficient light. I did note the lens hunting for focus more in low light, but i was able to manually focus when necessary. Finally I tried the TC on an old manual focus Nikon 100mm f/2.5 lens (adapted for use w/ current Nikon DSLRs) and liked the quality, but need to further try this combo to better discuss.
Some considerations: the 1.4x multiplication of focal length comes at the expense of one stop (e.g. f/2.8 becomes f/4-- not as quick). Also, the EXIF data (camera metadata) reports the f-stop and focal length as if the teleconverter wasn't there-- at least on the lenses i tried the TC with. So, when looking via view finder, I still saw "f/2.8", though I knew in reality that meant "f/4"-- a little confusing.
Anyway, I think the TC will be a helpfult tool, as i learn to use it more.
Just wanted to add somehting to the discussion that might be helpful to you as you ponder how to "stretch" your photography "wants" in light of your real-life budget... Take care.
Pablo

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