Nikon Teleconverter compatibility

From the Nikon site, AF-S Teleconverter TC-14E II [but the same caveat is on all 3 Teleconverters]

Compatible with AF-S and AF-I NIKKOR lenses except AF-S 17-35mm f/2.8D IF-ED, 24-85mm f/3.5-4.5G IF-ED, VR 24-120mm f/3.5-5.6G IF-ED, 28-70mm f/2.8D IF-ED and DX NIKKOR lenses.

Am I reading that correctly? No DX lenses are supported.

I'm somewhat disappointed that not only the lens I'm selling, the 24-120, isn't compatible, but also the one I've just replaced it with... a DX, isn't either.

I assume there's some sound reason for this - would anyone know what that is & what the penalty would be for ignoring the caveat?

I currently use a Nikon D5500 if that is relevant.

Answer

Teleconverters are designed for use with longer focal length lenses. Many are optimized for a specific focal length range of telephoto prime lenses.

There are both marketing reasons why this is so, but there are also technical reasons. Just as it is the case that zoom lenses with very wide focal length ranges must make compromises in image quality to allow that wide range, teleconverters designed for long focal lengths don't work as well with wider angle lenses.

Teleconverters magnify the center of the image projected by the lens. Every flaw of that lens is also magnified. It takes a very high quality lens to be able to take a teleconverter and still give high quality optical images. Most consumer grade zoom lenses are not up to the challenge. In most cases with such lenses, using the bare lens and cropping will give better results than using a consumer grade teleconverter. In the case of the three specific lenses listed in the question, purchasing a 70-300mm f/4-5.6 lens (pretty much everyone sells them) will get better results (at about the same cost) than putting a name brand (Nikon/Canon/etc.) TC on those lenses.

Most such lenses also have a slow enough maximum aperture that the additional stop (1.4X TC) or two (2X TC) added by the teleconverter means the maximum aperture of the lens/TC combo is too slow for the camera to be able to autofocus. Even if a lens/TC combination will AF, it usually does so much slower than the bare lens can.

Then there is the physical clearance aspect of it. Many teleconverters, particularly those made by camera manufacturers exclusively for use with specific lenses within their system, have lens elements that protrude into the rear of the attached lens. This isn't a problem with most long focal length lenses that usually have the rearmost element a ways in front of the lens flange. This is a considerable problem when the lens in question has elements just inside the lens flange or that protrude out the rear of the lens past the lens flange.

If you are bound and determined to use a TC with lenses such as those mentioned in the question, look into the third party TCs on the market. Most of them are the same line of products with various branding stamped on them and various versions in an effort to keep up with the communication protocols used by various camera and lens makers. Kenko is one such brand that distributes these TCs. They don't usually have elements that protrude and will usually allow APS-C only lenses, such as your Nikon DX lenses, to attach. (Most of them will not, however, allow unmodified Canon EF-S lenses to be mounted to them.)