central focusing wheel
/ˈsɛntɹəl ˈfəʊkəsɪŋ ˈwiːl/
n
English · central focusing wheel中文 · 中央调焦轮Español · rueda central de enfoqueFrançais · molette de mise au point
意味：Focusing ring for both the objective lenses; it is used to manually adjust the sharpness of the image.