1. An adaptor assembly for a 2-dimensional (2-D) digital camera with a variable 3-dimensional (3-D) photography assist arrangement, comprising: (a) a peripheral neck portion functionally detachably connected to lens barrel of the camera; (b) a rotatable and movable neck portion is permitted to pass through peripheral neck portion with a raceway disposed between the neck portion and the peripheral neck portion, and the neck portion operably connected to the lens barrel with an intervening space; (c) rolling mass bodies disposed in the raceway; (d) a head portion extending from the rotatable and movable neck portion; and (e) image capturing and transferring arms functionally connected to the head portion to capture a left image and right image resulting in a 3-dimensional image of a target-object at variable converging angles by movement of the rotatable and movable neck portion and/or the image capturing and transferring arms, and with a zero eccentricity between left and right images of the target-object.