Breathable membranes for lens assemblies are described. For example, a system may include a lens barrel having an inner channel extending from a first end of the lens barrel to a second end of the lens barrel. The lens barrel can include one or more inner lenses positioned within the inner channel. The lens barrel has a vent hole in a side of the lens barrel that extends from the inner channel to an exterior surface of the lens barrel. The system includes a membrane attached to the lens barrel and positioned to cover the vent hole. The membrane has pores large enough to permit nitrogen gas to flow through the membrane and the vent hole.