The optical design structure of FMA180 PRO is similar to that of FMA180. Its caliber is 40mm, focal ratio is f/4.5, and focal length is 180mm. Compared with the FMA180, it adds a finder-scope base and a 360 degree rotator, and upgrades the focusing device to a new integrated internal focusing system, which increases the stability of the focusing device and ensures its performance as a compact, high-quality small star lens.
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