Passive 3D Versus Active 3D - Which Technology is Best?
The practical choice of 3D-TV-technologies is really just between passive technology (polarized) and active technology (shutter glasses). Anaglyphic 3D is rubbish, and it's too early for parallax barrier home TV.
So here's a comparison table highlighting some of the differences between active and passive 3D:
| Passive 3D (polarized) | Active 3D | |
|---|---|---|
| With a flat-screen TV? | It's not the mainstream option that flat-screen-TV manufacturers are pursuing, but it is possible to get a passive 3D-capable TV such as the LG LD390 3D-capable passive LCD TV. | Definitely yes. There are plenty of LCD and plasma 3D-capable TVs with active-shutter technology. This is the mainstream of 3D television. You do need a special 3D-capable TV though - can't just use your existing telly. |
| With a projector? | Yes, but you need a special 3D-capable polarizing projector and a special silver screen that reflects the polarized light properly. The silver screen costs several times more than a standard projector screen. And of course you can't just use your wall (unless you happen to have an aluminium-coated wall). Passive 3D projectors are more for enthusiasts than the mass market. | Yes. Most 3D projectors on the market seem to be using active 3D technology. It does need to be a 3D-capable projector though. |
| Glasses options | You need 3D polarized glasses. Linearly-polarizing glasses for linearly-polarizing setups, and circularly-polarizing glasses for circularly-polarizing setups. | You need shutter glasses that are specifically designed to work with the TV. At the moment this means they need to come from the same manufacturer, though hopefully there'll be a compatibility standard at some point. Some companies are already selling shutter glasses that are supposedly cross-compatible, but I'm not sure how cross-compatible they really are. |
| Glasses costs | Cheap - just a few pounds for each pair of glasses. | Pretty expensive - typically £100 or more for each pair of glasses. If you want a pair for all your mates it'll cost a lot, and quite likely you'll need a whole new set if you replace the TV. |
| Can you tilt your head? | If it's using linear polarization, not really; if it's using circular polarization you can tilt it a fair bit. But you'll lose the 3D effect if you tilt your head too much. | You can tilt it a fair bit, but you'll lose the 3D effect if you tilt your head too much (same as for passive 3D with circular polarization). |
How does the quality compare?
Really it depends on the specific equipment you're looking at. My suggestion would be to read the reviews of any set of kit before buying it, or better still try before you buy. You'll hear people say things like: "active 3D TVs give you a headache", or "passive 3D TVs don't have such good resolution", but I suspect it comes down to the TVs in question.
For passive technology in particular, there are plenty of ways that it can be implemented. The passive LG TV mentioned above (The LD390) has lower 3D resolution than most active models when its running in 3D mode, because it splits the images for each eye across each line of pixels on the TV. But another manufacturer could potentially use that same approach, but on a screen with double the normal HD resolution.
For active technology, the refresh rate is a key factor - if it's too low, some people might notice the shuttering effect and get a headache.
Consider standard 2D TVs for a moment... A standard TV is 50 Hz (i.e. the pixel refresh 50 times per second), though a lot of more modern TVs are 100 Hz. Some people can notice the difference between a 100 Hz TV and a 50 Hz TV, some can't. Personally I don't think I can tell the difference.
I suspect that active 3D TVs are similar. Some manufacturers are offering 3D TVs with higher refresh rates like 200 Hz or 400 Hz. The higher the refresh rate, the less likely it is that the shuttering will be in any way noticable, but you might well end up spending extra money unnecessarily if you can't notice the difference anyway.