A lens device comprising: a diaphragm having an aperture value which is controlled to control a transmitted light quantity; an optical element having a light transmittance which is electrically controlled; and an exposure controlling unit which controls the aperture value of the diaphragm and the transmittance of the optical element in accordance with a brightness of a photographic subject to perform an exposure control, so as to obtain an exposure value corresponding to a proper exposure, wherein the exposure controlling unit changes at least one of the aperture value and the transmittance to set the exposure value which is included in a range of exposure value from a first exposure value which is determined by a combination of a state with a minimum value of the aperture value in a range of aperture value including an aperture value at which a maximum resolving power is obtained and a maximum value of the transmittance to a second exposure value which is determined by a combination of a state with a maximum value of the aperture value in the range of aperture value and a minimum value of the transmittance, and characterised in that the exposure controlling unit further performs a control to bring the aperture value at the exposure value close to the aperture value at which the maximum resolving power is obtained and change the transmittance at the exposure value so as to maintain the exposure value, when the aperture value at the exposure value is different from the aperture value at which the maximum resolving power is obtained and the transmittance at the exposure value is neither the minimum nor the maximum after setting the exposure value. a diaphragm having an aperture value which is controlled to control a transmitted light quantity; an optical element having a light transmittance which is electrically controlled; and an exposure controlling unit which controls the aperture value of the diaphragm and the transmittance of the optical element in accordance with a brightness of a photographic subject to perform an exposure control, so as to obtain an exposure value corresponding to a proper exposure, wherein the exposure controlling unit changes at least one of the aperture value and the transmittance to set the exposure value which is included in a range of exposure value from a first exposure value which is determined by a combination of a state with a minimum value of the aperture value in a range of aperture value including an aperture value at which a maximum resolving power is obtained and a maximum value of the transmittance to a second exposure value which is determined by a combination of a state with a maximum value of the aperture value in the range of aperture value and a minimum value of the transmittance, and characterised in that the exposure controlling unit further performs a control to bring the aperture value at the exposure value close to the aperture value at which the maximum resolving power is obtained and change the transmittance at the exposure value so as to maintain the exposure value, when the aperture value at the exposure value is different from the aperture value at which the maximum resolving power is obtained and the transmittance at the exposure value is neither the minimum nor the maximum after setting the exposure value.