A lens barrel movable between a collapsed position and a photographing position, and a picture taking apparatus using the lens barrel. The lens barrel has lens groups movable along an optical axis, a deformable mirror supported in the lens barrel, the deformable mirror having a reflecting surface which varies to vary its optical power, a picture taking optical system including the lens groups and the deformable mirror, and a driving mechanism for retracting the deformable mirror from a light path of the picture taking optical system when the lens barrel lies at the collapsed position, and inserting the deformable mirror into the light path of the picture taking optical system when the lens barrel lies at the photographing position.