Nighttime Reverse Effect. We do NOT claim that one way window film at night provides privacy. One way window film’s primary purposes are still to provide daytime privacy only, as well as to reject solar window heat and protect from 99% of damaging UV rays. At night, the one-way window film has a reverse mirroring effect. The brighter indoor lighting turns your windows into mirrors that don’t allow you to look out, but anyone outside in the darkness can easily see into your well-lit home. This is because at night there is typically less light outside (exterior) and people tend to brightly illuminate their homes in the dark evenings, making the interior of their homes brighter than the exterior. However, with correct floodlight placement, the nighttime reverse effect can be mitigated. Keep reading below to learn more.