An add-on lens assembly for a camera comprising: a lens housing (412, 812); a mounting mechanism (406, 806) coupled to the lens housing (412, 812) and configured to engage an attachment assembly of the camera; a lens (402, 802) mounted in the lens housing (412, 812), the lens (402, 802) defining a central optical axis and a lens plane normal to the central optical axis; a cam (430, 830) positioned adjacent to a portion of the lens housing (412, 812), the cam (430, 830) including a cam slot (432, 832) having a first length extending in a direction that is not parallel to the lens plane and being adjustable between at least a first cam position and a second cam position; a pusher (414, 814) configured to abut or nearly abut at least a portion of the attachment assembly of the camera, wherein a force between the pusher (414, 814) and the attachment assembly of the camera comprises a first force when the cam (430, 830) is in the first cam position and a second force when the cam (430, 830) is in the second cam position; a lock ring (408, 808) being rotatable between a first lock ring position and a second lock ring position; and a cam pin (410, 810) having a first end and a second end, the first end of the cam pin being fixed to the lock ring (408, 808) and the second end of the cam pin (410, 810) extending through the cam slot (432, 832) in the cam (430, 830); whereby rotating the lock ring (408, 808) from the first position to the second position causes the cam pin (410, 810) to navigate through the first length of the cam slot(432, 832), forcing the cam (430, 830) to transition from the first cam position to the second cam position and changing the force between the pusher (414, 814) and the attachment assembly of the camera from the first force to the second force. a lens housing (412, 812); a mounting mechanism (406, 806) coupled to the lens housing (412, 812) and configured to engage an attachment assembly of the camera; a lens (402, 802) mounted in the lens housing (412, 812), the lens (402, 802) defining a central optical axis and a lens plane normal to the central optical axis; a cam (430, 830) positioned adjacent to a portion of the lens housing (412, 812), the cam (430, 830) including a cam slot (432, 832) having a first length extending in a direction that is not parallel to the lens plane and being adjustable between at least a first cam position and a second cam position; a pusher (414, 814) configured to abut or nearly abut at least a portion of the attachment assembly of the camera, wherein a force between the pusher (414, 814) and the attachment assembly of the camera comprises a first force when the cam (430, 830) is in the first cam position and a second force when the cam (430, 830) is in the second cam position; a lock ring (408, 808) being rotatable between a first lock ring position and a second lock ring position; and a cam pin (410, 810) having a first end and a second end, the first end of the cam pin being fixed to the lock ring (408, 808) and the second end of the cam pin (410, 810) extending through the cam slot (432, 832) in the cam (430, 830); whereby rotating the lock ring (408, 808) from the first position to the second position causes the cam pin (410, 810) to navigate through the first length of the cam slot(432, 832), forcing the cam (430, 830) to transition from the first cam position to the second cam position and changing the force between the pusher (414, 814) and the attachment assembly of the camera from the first force to the second force.