Light trespass

In previous "view from your app" images we have only had a few examples of light trespass: when light illuminates something it is not meant to illuminate.

My colleague Catalin-Daniel Galatanu sent me an excellent example of light trespass from Iași, Romania. In the photo below, you can see a residential building that is brightly illuminated by the spill light from church facade lighting:

Light trespass by Catalin-Daniel Galatanu is licensed under
a Creative Commons Attribution 4.0 International License.

Catalin used his images to calculate the luminance of the facades, and got the following result:

Light trespass luminance by Catalin-Daniel Galatanu is licensed under
a Creative Commons Attribution 4.0 International License.

The lit areas have a luminance of 2-4 cd/m². To calculate the illuminance on the windows it would be necessary to know the albedo of the building, but with a rough guess of 0.7 that would imply around 15 lux. I think it would be pretty unpleasant to have such a bright light shining into either your bedroom or living room! Catalin points out that in addition to the light in the room, the people living here have lost not only the view of the stars from their window, but they wouldn't be able to enjoy their view over the city at night, due to the unpleasant glare.

It's important to stress that there's absolutely no reason that it has to be this way. With more carefully directed lighting, the church could be illuminated with limited or no spill light. Furthermore, it's not necessary to shine so much light on a facade for it to have the impression of being illuminated. I hope to soon be able to share a great example of how churches can be more effectively lit (paper in review).