需要手動伸縮. but it is much easier than I originally think. You just use your left indexs finger and thumb to lightly moves it (if you need, but you don't really need?). It is virtually the same as using the old same "push-pull' zoom SLR lens.

型仔......

請問是否需要手動伸縮？還是個 tube 本身已有回彈力？