When the camera has to be placed behind a window that is subject to reflection, the best way to avoid the effect of reflection (glare) on the window is to stick the camera on the window.

Unfortunately there are no magic tricks, if your eye can see the reflection so will the camera. The only variables that one can play with are:

  • distance camera-glass: the closer the camera, the fewer the reflections. Ideally, glue the camera to the glass 
  • indoor light. If the exterior is darker than the interior, the reflection will be more apparent. Avoid using a very bright screen behind the glass, reduce the brightness as much as possible.
  • clean glass: dust or other films may increase the reflection 
  • polarized filter (like one of those): it minimizes reflections but does not eliminate them. You also need to rotate the filter to find the best result