Want to see how much reflected light your polarizing filter eliminates from any scene? You can easily visualize this light using an image editing program like Photoshop.
Photography enthusiast Michal Zalewski captured the “reflected light” photograph above showing a room in his house. He started by shooting two photographs of the scene. The first was shot with a polarizing filter killing the reflections on the lower surfaces:
Keeping the camera stationary, he also captured a frame showing the scene with that same filter rotated 90 degrees. This shows the scene with those reflections still present:
He then subtracted the RAW 16-bit photographs “from each other” in order to capture “just the information about the reflections in the scene”:
At this point, you can do various things with the information you have, including selective colorization, dodging, burning, etc. Here’s the photograph with the reflected light turned into monochrome:
…and the same photograph with the scene in monochrome and the reflected light in color:
Zalewski says it wouldn’t be difficult to build some kind of rig that could automatically gather information about reflected light for you, but he has yet to find a useful photographic application for the technique.
Image credits: Photographs by Michal Zalewski and used with permission