Who has not thought that it is a stupid rule that you’re not allowed to use flash in museums? I’ve seen this in several museums and always wondered what the reason was for this ban to exist. I would have understood if they banned all photography in general, due to copyright issues or a desire that no images taken within it, encouraging people to visit the museum rather than visit them virtually. While some do it, the prohibition of using flash is always present and there has never seemed to have been a proven scientific basis that this type of shot with light has any effect on the exhibits. The rumor was that it was just a baseless rule that came from long ago, and was passed from hand to hand until present day.
But apparently this is true and the flash really does have an effect on the paintings and museum exhibitions. Someone had the same doubt as me and asked this question on Skeptics.SE where the replies were very revealing.
Turns out the Xenon lamps present in flash tubes are commonly used in accelerated aging tests on different products. When a device is launched ensuring a lifespan of 100 years, it does not mean this product has lasted 100 years, but instead has used a processes that accelerates the deterioration process, and xenon lamps are a classic in these tests.
The bursts of light flashes cause certain pigments to break and lose their vibration and color. Imagine leaving La Gioconda in the sun all afternoon. Some discoloration will be noticed, same as electronics stores that have the sun rays hit on all the equipment and you can clearly notice that the piano black color of the TV has gradually become exposed and gradually turned to a ashy gray color.
Now, simply shooting your camera will not cause visible damage. Ten shots of your flash will not either. Then think of the millions of annual visitors that a museum has, and the number of shots that each person takes. The deterioration really starts to become visible, and would be the same effect as getting hit by the sun’s rays all afternoon.
So next time you see a sign not to use the flash, remember it’s not a stupid rule, but something very important that we should all collaborate on.