After speaking with Bobster directly we were informed that these photochromic lenses are UV activated. Thus, if you use a faceshield that does not allow UV Rays to pass through it then there is no way to trigger the change to occur on the Bobster lenses. Also, the lenses that come with these goggles are already considered to be a dark smoke, and they would only get darker. They do not become lighter at all, and the overall change in tint is not as great as something like the Bell Transitions SolFX Photochromic Face Shield which goes from a clear to a mellow smoke (between light smoke and dark smoke).