Nikon currently makes four teleconverters:
- TC-14E increases focal length by 1.4x, and lowers maximum aperture by one stop. The original TC-14E was marked AF-I, the TC-14EII and the redesigned TC-14EIII are marked AF-S.
- TC-17E increases focal length by 1.7x and lowers maximum aperture by one-and-a-half stops. There has been only one version of this converter.
- TC-20E increases focal length by 2x and lowers maximum aperture by two stops. The original version was marked AF-I, a second version (II) AF-S, and then it was redesigned optically to create the current TC-20EIII.
- TC-800-1.25E ED comes with the 800mm f/5.6 and increases focal length by 1.25x and lowers the maximum aperture on the lens to f/7.1.
Technically, the TC-17E is a II model, though there are no optical or performance differences between the I and II models of TCs that I know of, so I generally make no distinction between I and II models. The TC-14E and TC-20E come in I, II, and III models, and you definitely want the III model of either of these, which have revised optical characteristics that make them far better than the previous versions.
The questions that come up are what lenses can or should you use these converters on, and what are the drawbacks (other than aperture loss)?
Here are my recommendations for lenses on which these teleconverters perform well on:
- TC-14E III: 70-200mm f/2.8G or f/2.8E, 70-200mm f/4G, 200mm f/2G, 300mm f/2.8, 300mm f/4E, 400mm f/2.8G or f/2.8E, 500mm f/4G or f/4E, 600mm f/4G or f/4E
- TC-17E: 70-200mm f/2.8G or f/2.8E, 200mm f/2G, 300mm f/2.8G, 400mm f/2.8G or f/2.8E
- TC-20E III: 70-200mm f/2.8G or f/2.8E, 200mm f/2G, 300mm f/2.8G, 400mm f/2.8G or f/2.8E
I've also had a reasonable experience with the following, but test before relying upon it:
- TC-14E: 200-400mm f/4G, 200-500mm f/5.6E
- TC-17E: 500mm f/4G, 600mm f/4G
- TC-20E III: 200-400mm f/4G, 500mm f/4G, 600mm f/4G
As you can tell, those are pretty small lists. Moreover, I'd strongly suggest that you perform AF Fine Tune if you're going to use a converter: the additional mount involved can add a tolerance change that makes precise focus needing adjustment.
One benefit that people don't realize about teleconverters is that the minimum focus distance stays the same. If you do a lot of very close telephoto work (e.g. hummingbirds in blind shots), there may be an advantage to using something like the 300mm f/2.8 with a TC. First, the 300mm is quite tolerant of converters, but to the point: focus distance stays at 2.3m, meaning you could have a 600mm equivalent that focuses down to less than eight feet.
Here are additional articles about teleconverters in this section: