This year Korean electronics giant LG Electronics is being adventurous when it comes to 3D. Instead of using the same technology as the other manufacturers — indeed, the same as it used itself last year — it has taken a radically different approach in its new lines of 3D TV, including this 47LW6500.
The essence of 3D TVs is in delivering, somehow or other, separate vision to each of your two eyes. Since last year the method for home TVs has been sequential — that is, the image for your left eye flashes on the screen, then an instant later it disappears to be replaced by the image for your right eye.
To achieve this eye-by-eye delivery, you wear special glasses with the lenses made of liquid crystal screens. These flash between opaque and transparent in time with the pictures appearing on the screen. If all works well, then each eye will see only the image intended for it.
When 3D TVs first appeared last year, “all working well” was the difficult part. Most TVs had quite a bit of leakage of image from one eye to the other, leading to ghosting. Your left eye would see something intended for the right and vice versa, so objects on the screen would appear to have translucent ghosts beside them.
In addition to being very inaccurate, this tended to reduce the effectiveness of the 3D.
Plasma TVs seemed to be quite a bit better on this front than LCD ones, and there was even some variation between LCD ones.
That was last year. This year, as you’ll see from the models reviewed in this issue, most brands have persisted with shutter glasses, and some seem to have improved their performance a great deal. But with this TV, LG has gone in a different direction.
It doesn’t use shutter glasses at all, but passive glasses. These are like those used at most 3D cinemas. In fact, LG forgot to pack some into the box with this review TV, and I found I was able to use the actual cinema ones to just as good effect. (I was provided the real ones later, so what follows is based on the full LG kit.)
With this TV, rather than the left and right eye images being displayed in sequence, they are both shown at the same time. The separation is achieved by means of polarisation. Light waves have a twist, either clockwise or counter clockwise. Filters can allow through either one or the other.
Half the screen’s pixels are filtered to allow only the light with a clockwise twist to emerge, and the other half allow only the anticlockwise light to be seen. Matching polarised filters in the glasses let each eye see only the half of the image intended for it.
Now if you read the last paragraph closely, you will realise that with 3D content, each eye only sees half the pixels. But which ones?