It wasn’t that long ago that when the words ‘home theatre’ came up, people envisioned grand palaces, presidential mansions and celebrity homes. However, a lot has changed.

To paraphrase a line from the Kevin Costner film Field Of Dreams: if you build it, they will come. And so they have.

Fierce competition between manufacturers of home theatre projectors and screens has resulted in a flood of high-quality gear at a modest price most incomes can bear.

So, with my diabolical plan of ‘a big-screen theatre in every home’ becoming plausible, what now?

If you are going for the authentic cinema experience in your home, why not do it all? I’m mainly talking 3D, but there is a right and a wrong way to go about it. Here is a realistic rundown on having a functional and practical 3D home theatre that you’ll never tire of.

3D in a nutshell
There are two basic types: passive and active.

Passive 3D uses two projectors whose output is combined in a single image. One projection has a vertical orientation and the other is horizontal.

Corresponding with this are the passive 3D glasses: one lens is vertically aligned and the other is horizontal. This is the inexpensive “throw away” type normally used in large theatres.

The other basic type is active 3D (aka active shutter), which is the norm in most home theatre systems. It shows alternating horizontal/vertical images usually at a rate of 120 frames per second (60 per eye) using a single projector.

The glasses for these systems employ liquid crystal technology that effectively ‘shutters’ or blocks the image from the left or right eye in sequence with the desired frame at the particular 1/120th of a second. At this high rate, human eyes do not register the flickering in the lenses.

Active shutter 3D glasses require a power source and are quite expensive compared with the glasses used at the movies.

As cool as active shutter 3D technology is, it has its drawbacks:

• Apart from being expensive, the glasses are prone to malfunction because they are electronic devices.
• Each eye is blacked out for half the time, so the viewer gets only 50% of the brightness.
• Although the eyes do not register the flickering, the visual system ‘knows’ something isn’t quite right and struggles to maintain equilibrium. This means discomfort, and viewers generally don’t want to ‘live the 3D experience’ any longer than the duration of an average film.

All this is why many AV specialists feel that a passive 3D system would be better. The image is brighter, the discomfort is exponentially less, and the glasses are affordable for the whole family rather than for the privileged few.

The only obstacle has been the prohibitive cost of two projectors and a video processor. However, the situation is now a lot more in favour of the home theatre enthusiast.

Practical home theatre 3D
One of the more amusing quotes I read at the beginning of the oft-cited ‘home theatre 3D revolution’ was: “Despite all the industry hype, someone forgot to tell the customers about it.”

Manufacturers wondered why their ‘3D without the glasses’ flat panels flew off the shelves with the speed of a tricycle in the Grand Prix. Yet nobody seemed to ask: “Does everyone want 3D on a 24/7 basis?”

The answer is a resounding no. People like 3D because it is a special-occasion product for certain films, and the ‘impressing your friends’ factor doesn’t hurt either.

I love watching Avatar in 3D on a Friday evening, but having a 3D image running for hours on end is physically draining. Likewise, I have little interest in turning the six o’clock news or a Dick Smith Foods commercial into an immersive 3D extravaganza.

However, a more significant deterrent than repetition-induced boredom is eye strain from active 3D glasses.

All this culminates in the (still unanswered) question: what’s the solution when bringing 3D cinema into the home? That answer is ‘stacking’.

Make it happen
The solution is simpler and more cost effective than you might think.

An emerging technology on the market allows an end-user to stack multiple images into a single image. But it can’t be done just by lining up a couple of projectors – they must be synchronised down to the pixel by using a stacking processor. This device contains software that allows you to perfectly overlap images from multiple projectors.

Why? It’s done for superior brightness, which is essential for 3D, and for the stereoscopic array necessary for a passive 3D presentation.

The typical home theatre projection screen does not have brightness levels of more than 3000 lumens. Professional-grade projectors with brightness levels of 5000 lumens or more come with a five-figure price.

By employing two relatively inexpensive projectors and coupling them with a stacking processor, end-users get the same brightness levels as produced in a professional set-up. (This is important, as we are trying to match the qualities of a movie theatre.)

It needs one more thing to make it perfect – polarised material, which keeps the wavelengths of the vertical/horizontal images separate. This allows the eyeglass filters to assign the image to each eye with maximum clarity.

In addition, polarised material has superior reflectivity that will enhance the brightness and compensate for tinted 3D glasses worn in a darkened room. Without polarised materials, a good passive 3D solution would be almost impossible.