Barlow (also called teleconverters, also called telephoto pitch mirror), it is a optical accessory is mounted between the lens and the camera body. It can enlarge the image.
The magnification lens has a different amount of radiation. A 2 x zoom lens doubles the size of the image, that is to say, it can double the focal length of the lens after installing it. If the magnification lens attached to the 50mm lens, the image will be the same as the size of the image taken by the 100mm lens; if you put it on the 200mm lens, you will get the 400mm camera image size, etc..
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