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3D films and photosensitive epilepsy
Can 3D films trigger seizures in people with photosensitive epilepsy?
Photosensitive epilepsy affects up to 5% of people with epilepsy. Photosensitive triggers include certain rates of flickering images or light. In general, seeing a film at the cinema is unlikely to trigger seizures. However, following the recent popularity of 3D blockbuster, Avatar, NSE asked photosensitive epilepsy expert Professor Graham Harding whether 3D films could trigger seizures in those who are photosensitive.
Professor Harding says:
"There are relatively few cases of photosensitive seizures in cinemas. The frame rate of normal cinemas is 24 frames per second, which would produce noticeable flicker and so be a risk to photosensitive people. However, the intensity in the cinema is very low (about one hundredth of a television set).
"With ‘real 3D’ films, three images are projected, at a combined rate of 48 flashes per second. Because the projected images are polarised – that is, aimed at each separate eye – that is 24 flashes per second to each eye. If one assumes that the polarising reduces the light output by fifty percent there should be even less risk of a seizure trigger for people with photosensitive epilepsy.
"This means you are only getting half the intensity of a normal cinema, but equally everything else in the cinema has a similar reduction so the contrast remains the same. It appears that this is like wearing sunglasses in a normal cinema."
