Access to a new dimension
3D movies are becoming popular. 3D televisions are also now on sale. But 3D is not accessible to many people with a disability. Most 3D technologies use special glasses. Without the glasses the images can be a blur. There are not many glasses yet that can be worn with another set of glasses to improve vision. People with some types of vision impairment might not be able to see the 3D effect at all. 3D can also make it difficult to add subtitles to a movie. People should test a 3D television carefully before buying one.
Posted by: Jennifer Vesperman, on 23/04/10
Many people enjoy the novelty and added realism that the 3D effect can produce
3D movies like Avatar, Clash of the Titans and Alice in Wonderland have recently enjoyed great success. Many people enjoy the novelty and added realism that the 3D effect can produce. The entertainment and consumer technology industries now see 3D as the future of film, television and video games. The first 3D televisions hit Australian store shelves this week. But 3D does present difficulties and challenges for many people with a disability.
There are four different 3D video technologies. All work differently. Three of them require viewers to wear special glasses. Without the glasses the picture can be a blur. The 3D glasses come in three types:
- Colour-separation glasses with two differently coloured lenses. These give a different image to each eye by filtering colours.
- Polarised glasses that look a bit like sunglasses. These provide different images by each lens allowing differently polarised light to pass.
- Active-shutter glasses. These rapidly block light to each eye in turn. Each eye only sees the image intended for that eye. Active-shutter glasses are electronic and require a battery. Most also require a little bit of manual adjustment when you first put them on.
Problem for some people
The glasses can darken the image that you see. It means that a 3D movie or television program needs to be displayed much brighter than normal. 3D glasses also cause issues with colour balance and contrast which can be a problem for some people with vision impairment. If you require corrective lenses, there are not many 3D glasses available yet that fit over spectacles.
Even for those with perfect sight, 3D glasses can reduce image quality. Colour-separation glasses mean that there are colours that cannot be shown correctly. Polarised glasses reduce the overall image quality.
The 3D technology that does not require glasses is marketed as Auto 3D. Auto 3D televisions have a special coating that shows each eye a slightly different image. The problem is that the “sweet spot” where you can see the 3D picture is limited. You need to be sitting at the right angle to the screen. Some Auto 3D televisions have multiple zones to accommodate more viewers. But the larger the TV, the further away you need to sit.
All 3D video requires good binocular vision. You need to be able to see the world in depth through parallax. Parallax is the difference between the perceived position of an object as viewed by the left eye compared to the right eye.
Risk permanent damage
There is some concern that 3D TV will lead to an ongoing problem called binocular dysphoria. The brain learns to rely solely on the parallax cue, not other cues to judge depth. Some people are concerned that viewers will risk permanent damage to their vision.
Manufacturers of 3D televisions also warn that people who have a family history of epileptic seizures or strokes should consult a medical specialist before using a 3D television. They also warn viewers to stop watching if they experience symptoms like:
- Altered vision
- Motion sickness
- Eye strain.
If you’ve got a vision impairment that prevents you from seeing depth normally, 3D video will not be accessible to you. The image will probably look a lot worse than 2D broadcasts.
Captioning is also a challenge in the 3D era. The placement and type of text is more difficult than 2D.
Story is told in imagery
Some people are also worried that the move to 3D will cause the movie industry to put more of the story in the visuals. Already, a lot of story is told in imagery. Audio description can assist those with vision impairment to understand the story as long as there is enough dialog. But if the story is told too much with visuals it becomes less enjoyable for those who rely on audio description.
But at the moment, 3D is being used as a gimmick to add a little more excitement to movies. You aren’t going to miss much by watching them in 2D. Hopefully it will stay that way, or perhaps boffins can find solutions to the many accessibility problems.
Anyone worried about accessibility should get a thorough demonstration of a 3D television before buying. Thankfully most stores are more than happy to provide demonstrations.
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