[Alghranokk]

It does not seem to be using a material we would normally consider appropriate for photograpic film. The article mentions: "multiple thin layers of an oil paint pigment called rose madder"

If i understand the principle correctly, the captured light would simply slowly fade exposed portions of the "film" over centures, eventually resulting in a faint negative of the sum total of the scenes witnessed.

Exposing the film to light at that point, one kiloyear from now, would probably do nothing, unless you left it exposed for a couple decades to direct sunlight.