Originally Posted by
offerendum
At Sistine Chapel they were very strict during my last visit. But sometimes there are too much rule-breakers

Photographing with flash inside the chapel is a nerviness as it can destroy the paintings

Likewise, no photography at the Last Supper in Milan. Only 25 people at a time are allowed inside, because the breathing of larger crowds produces gasses harmful to the work (it is a mural, not a painting).