Teleconverter / Extender
Teleconverter · Lens & optics
An optical element placed between camera and lens that multiplies the focal length at the cost of maximum aperture.
Common converters are 1.4× and 2×. A 1.4× converter on a 300mm f/2.8 gives 420mm f/4. A 2× gives 600mm f/5.6. Quality loss is minimal with high-end converters and sharp prime lenses. Not all lenses are compatible with all converters.
Tools that help with this: