Relatively easy to use.
There are two types of Canon teleconverters, one is 1.4× and the other is 2×.
For 1.4×, the focal length of the lens can be increased to 1.4 times the original, and the maximum aperture also becomes 1/1.4; for 2×, the focal length can be increased to the original 2 times, and the maximum aperture also becomes 1/2 of the original.
Note:
1. Not all EF mount lenses can use teleconverters.
2. Even if it can be used, some functions of the original lens will be lost.
3. Using a teleconverter can bring convenience, but it also reduces the image quality of the original lens.
Additional answer:
From the picture, this is Canon’s second-generation 1.4× teleconverter, which has been discontinued and has been replaced by the third-generation 1.4× teleconverter.
The third generation 1.4× teleconverter is suitable for the following lenses:
EF 135mm f/2L USM
EF 180mm f/3.5L USM Macro
EF 200mm f/2L IS USM
EF 200mm f/2.8L II USM
EF 300mm f/2.8L IS II USM
EF 300mm f/2.8L IS USM
EF 300mm f/4L IS USM
EF 400mm f/2.8L IS II USM
EF 400mm f/2.8L IS USM
EF 400mm f/4 DO IS USM
EF 400mm f/5.6L USM
EF 500mm f/4L IS II USM
EF 500mm f/4L IS USM
EF 600mm f/4L IS II USM
EF 600mm f/4L IS USM
EF 800mm f/ 5.6L IS USM
EF 70-200mm f/2.8L IS II USM
EF 70-200mm f/2.8L USM
EF 70-200mm f /4L IS USM
EF 70-200mm f/4L USM
EF 100-400mm f/4.5-5.6L IS USM