Reversible electrodeposition of metallic bismuth onto transparent conducting substrates was studied with interest in the electrochromic phenomena produced by plating and stripping a thin metallic film. Different bismuth films were prepared potentiostatically by applying potential steps of different amplitude (whilst maintaining the electric charge at a constant value), and the change in transmittance was followed in situ simultaneously during the electrodeposition process, A large change of transmittance was observed for constant charge films prepared at different deposition potentials. As the absorbance is related to the deposition charge (amount of metallic bismuth electrodeposited), changes in optical properties of equivalent films must be related to large changes in film morphology; this was corroborated by scanning electron microscopy. The effect of copper additives was also analyzed : this produced changes in film morphology, leading to bidimensional deposition being predominant over the tridimensional process.