A teleconverter (sometimes called tele extender) allows you to increase the apparent focal length of a lens, giving you a greater telephoto effect than a lens alone. A teleconverter is basically a magnifying lens that is placed between the camera body and lens. Teleconverters are favorite accessories of nature and wildlife photographers, because they allow them to extend the photographic reach beyond what might be safe when on safari or in an unfamiliar location. In general, wide-angle prime and zoom lenses are not compatible with teleconverters; which makes sense, since you’re using a teleconverter to increase your reach—and you’d likely start out with a longer focal length lens to begin with. Using a teleconverter is an affordable option when you want to increase your photographic reach without having to purchase new super-telephoto lenses.
Yongnuo YN-1.4X III extender is a great alternative to the Canon EF 1.4X III teleconverter offering pretty similar performance for 3 times less price. Yongnuo’s version like Canons also packs 7 lens elements into 3 groups and reduces the lens maximum effective aperture by one stop. This is common for 1.4X teleconverters, while 2.0X teleconverters reduce the lens maximum effective aperture by two stops.
Just like the Canon 1.4x III Extender, this lens is only compatible with the longer Canon L lenses (135mm and up). You can’t use it with the 100mm 2.8 Macro L for instance. That’s because of the protruding optic that will not allow you to mount this on anything but the longer L lenses.
Yongnuo YN-2.0X III teleconverter is a great alternative to the Canon EF 2X III teleconverter offering pretty similar performance for 3 times less price. Yongnuo’s version like Canon’s also packs 9 lens elements into 5 groups and reduces the lens maximum effective aperture by two stops. This is common for 2.0X teleconverters, while 1.4X teleconverters reduce the lens maximum effective aperture by one stop.
Featuring electronic communication from the lens to the camera, this teleconverter allows for all standard functions of the lens to work as normal, including autofocus and image stabilization.