What are teleconverters and how do they work?
Tele-converters are handy lens add-ons that multiply the focal length of the lens they are attached to. They can be mounted in between the camera body and lens (typically a telephoto lens) and increase the focal length of the lens which they are attached to.
By how much is dependent on their power, which is stated as a factor. E.g. a 1.4x teleconverter multiplies the original focal length of a lens by 1.4. As a result a 100mm lens would turn into a 140mm lens, a 200mm lens would turn into a 280mm lens, and so on. Most common are 1.4x or 2x converters, but occasionally converters as strong as 3x can be found as well.
Why am I telling you this in a macro blog? Well, the beauty of these converters is that their power not only applies to the focal length of regular lenses, but to the magnification ratio of macro lenses just as well!