A lens barrel assembly for use with a digital still camera includes an outer barrel having a front end and a rear end. An inner barrel is inserted in the outer barrel in an optical axis direction. The outer barrel moves forwards relative to the inner barrel, to shift between a short size position and a long size position, and when in the short size position, shifts from the inner barrel at a smallest shifting amount, and when in the long size position, shifts from the inner barrel at a largest shifting amount. A vent is formed in the outer barrel, and disposed close to the front end. A filter is water-impermeable and air-permeable, and secured to the vent in a closed manner. Also, a vent cover is secured to the outer barrel, for covering the vent.