Technical Information
They are constructed with metal bayonets, and engineered plastic ends. There are no moving parts, other than the lens latch lock. Two generations of the extenders exist, the older 1.4× and 2×, plus the newer 1.4× II as well as 2× II. The newer II versions have weather-sealing and anti-reflective surfaces inside the extender body. The optical construction of the 1.4× versions are a of five-element design. Both 2× versions use seven elements, although the optical formula of the II version is different, to improve optical performance .
Read more about this topic: Canon Extender EF
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