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Understanding the 3D technologies.

We have 2 eyes, which means that when we view the world, we see it from two slightly different angles. This produces two slightly different images that we are looking at. Our brain simultaneously processes these two images, combining them into one image giving the perception of depth.
Conventional filming and photography methods shoot the image from a single lens, producing a single image. This means that when we watch something on TV or look at a photo, there can be no impression of depth, the picture looks flat.
3D film and photography have solved this by recording the image using two lenses to simulate our two eyes. The lenses are set side by side 6.4cm away from each other, just like our eyes. The glasses which come with the 3D technologies allow the left eye to only see the image from the left camera lens and the right eye to only see the image from the right camera lens. These two images can then be processed by the brain in exactly the same way as it could if you were really looking at the object in real life, giving the perception of depth.
The first has been around for many years. If you’re old enough you may remember the terrifying movie Jaws 3D, ‘scarred me for life’. Anyway this technology is called ‘Anaglyphic 3D‘. It doesn’t require a special TV to watch these movies, only special glasses. You’ll know them, 2 different coloured lenses. The left eye having a red tinted lens and the right having a cyan tinted lens. The way it works is each of the coloured filters in the glasses removes the opposite tinted image so that each eye only sees the correct image. The brain processes these images to create the 3D effect.
This technology has the drawback of not producing genuine colour reproduction, lowering the quality of the image. Whilst this is still currently in use with the recent release of films and video and some games in anaglyphic 3D, it is the lowest quality 3D image available.
Next we come to ‘Active 3D TVs’. These are the TVs manufacturers want us to go for. A way to remember the name is because the glasses are actively working to help produce the 3D effect to the viewer. This technology works by wearing a pair of active shutter glasses that are synchronised with the TV using infrared. The 3D picture produced on the TV screen switches many times a second between what the left eye and right eye should see. So when the left eye’s image is on the screen the left eye of the glasses becomes transparent and the right eye of the glasses goes dark, preventing the right eye from seeing the image. This process then reverses when the right eye’s image appears on the screen, with the right lens becoming transparent and the left lens going dark.
This technology gives a wonderful full HD quality picture. The main drawbacks here are the glasses. Some of them are weighing in at 2.2 ounces (62 grams) due to them needing batteries to work. That weight can get quite uncomfortable after a short while. And secondly the cost of the glasses each pair can cost between £50 and £120.
Other key notes:
  • You get a wide viewing angle with these TVs approximately 120º that’s 60º either side of centre.
  • Full 1080p HD image in every single frame.
  • The active glasses do not need to be worn perfectly horizontal; they work just as well at any angle, so you can slump comfortably in front of the TV without losing picture quality
Finally we have the ‘Passive 3D TVs’. These work in a very different way. As the name suggests, these glasses receive the TV picture but don’t actively have to do anything. Light travels in waves which can move and shine in any direction. A polarizing filter in the TV aligns the light to either a horizontal or vertical orientation. Half of the lines on the TV screen will be polarised to allow the horizontal light through, and half of the lines will be polarised to allow the vertical light through. So, for example, on a TV with 1080 horizontal lines, 540 of these lines will be alternately polarised in each of the directions, effectively interlacing the left and right eyes’ images. Both images are on the screen at the same. The viewer watches the TV screen wearing glasses with the corresponding polarised filters. Because the horizontal polarised filter in the glasses will not allow the vertical polarised light to come through, and vice versa, each eye sees only the correct image from the screen.
Again this technology gives a wonderful HD quality picture (not full HD) and many have said between the 2 technologies active and passive this technology is by far the superior 3D technology. These TVs also have glasses that are as light as the Anaglyphic 3D tinted lens glasses.
Other key notes:
  • Glasses are cheaper to purchase and replace, this makes it a lower start-up cost for large families, or places where many people will want to watch the TV at the same time. Also less of a worry for families with small children as they are harder to damage in such a way as to make them useless and will cost very little to replace.
  • Glasses don’t need to be recharged so you won’t have the frustrating experience of going to watch TV and finding that the glasses have run out of battery.
  • The glasses are light weight so Ideal for longer sessions of watching 3D content.
    If you have loss of vision in one eye, they will not be able to perceive the 3D effect. It is important to note that if you are watching 3D TV with other people, they would still need to wear the corresponding glasses otherwise they would see both images overlapping each other on the screen, making a blurry and unclear image.
    Similarly, if you have one eye which is stronger than the other, the 3D effect could be reduced.
    If you wear prescription glasses which are already polarised, they will interfere with the Passive glasses. You should remove them before trying to watch a Passive TV system.
    Apart from the known problems above with watching 3D, a small number of you that are unable to see the 3D effect on TVs. There is no clear explanation for why this should be the case and it seems not to be linked to any particular disability, so it’s important for you to check that you can see the 3D effect on a 3D TV before purchasing.
    For a device to display or transmit Full HD in 3D content it must have a HDMI 1.4 port and be connected using a High Speed cable. Devices such as 3D TV’s, 3D projectors and 3D Blu-ray players will all have a HDMI 1.4 port so that they can utilise their 3D capabilities. Whilst there are a number of devices that will be able to transmit 3D content without a HDMI1.4 port these devices will not be able to transmit 3D in Full HD, instead they will have to transmit their 3D content in 1080i or 720p.
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