I dont know the answer to you question but if your pigeons started to body moult and start throwing flights like confetti akin to the light system I would be concerned. If I were in your situation I would make up some screens which I could easily place in front of the loft in the evenings and remove in the mornings.
I would make the screens out of a material like this, cheap and light http://www.primrose-london.co.uk/rush-screening-c-378.html