In terms of the optical phenomenon that occurs, it’s not different at all.  All a pair of 3D glasses does is filter light in different ways to allow us to register the two separate images on the screen as a single picture with depth. But if the word 3D conjures up visions of old pictures of audiences packed into dark theaters with flimsy cardboard glasses,  you are in for a big surprise. The original glasses employed a method known as “anaglyph,” which used different-colored lenses (usually red and green) to filter two false-color images into one. The result - though impressive at the time to a world that had never seen anything beyond a flat image - was an image that had a lower resolution and was slightly discolored to the discerning eye. While still occasionally in use, anaglyph has since evolved into the two 3D technologies commonly used in today’s 3D television, “active 3D” and “passive 3D.”

The names might seem a little misleading, but the terms have little to do with your level of participation while watching 3D TV and more to do with how the glasses themselves operate. Passive 3D uses polarized lenses to create an effect similar to that of anaglyph, though with far better and brighter image quality. While battery-powered active 3D glasses use an active liquid crystal shutter system that opens and closes about 120 times a second. The shutter system alternates blocking each eye for a split second, while syncing with the television with an infrared or radio frequency signal.

Watching 3D television requires three essential ingredients. First, you need content that’s being transmitted as 3D. Whether it’s 3D television programming, a 3D Blu-ray or a 3D game, if it’s not presented in 3D, no piece of equipment will make it so.

Second, you need a television that supports 3D technology. And, finally, you need 3D glasses that will help your eyes convert the image on your television screen from two separate images into a single three-dimensional image.

The types of media content available in 3D is an ever-growing list, but some of the most popular are television programming, 3D Blu-ray, a growing number of 3D video games and some of the very first 3D Internet streaming content, including user-generated entertainment. Content can be divided into two categories, “native” and “non-native.” Native 3D content is material that was shot in 3D using two cameras as described above, while non-native content was originally shot in a conventional two-dimensional format and converted to a three-dimensional format later. There has been some debate and variance as to the quality of non-native 3D content. Conventional wisdom tends to favor native 3D, when available, as the optimal content to enjoy the full experience that 3D TV has to offer.

If you’re wondering whether you’ll need to replace your conventional HDTV to view 3D content, the answer is most likely “yes.” 3D television signals essentially consist of two different images, so handling both requires special hardware not found in most HDTVs. In addition, active 3D television sets contain equipment to handle the infrared or radio frequency they use to communicate with active glasses. On the other hand, passive 3D television sets have a special screen “retarder” that helps enable the passive glasses to work.

However, 3D television is not just for 3D programming. You’re just as able to watch conventional two-dimensional programming on a 3D TV as any other HDTV.  And today’s newest 3D television sets also provide the very best 2D viewing experience possible — just don’t expect them to magically turn your old 2D content into 3D. Remember, the content source must be 3D as well.

Are all 3D glasses the same? If you’ve been reading carefully, you’ll already know the answer is no. There are — you guessed it — both active and passive glasses.  We’ve already discussed how they work differently above (reminder: active is the one with the battery and lightning-fast liquid crystal shutter, passive uses polarization), but how do you know which one is right for you? Each has its pros and cons, so it depends on what’s most important to you. They both have their fans, not only among consumers but also among manufacturers.  Most top television companies make only 3D TVs using one system or the other, although several embrace both technologies. The advantage of an active 3D system is superior image resolution. Because the shutter system is based on alternately shielding our eyes individually, the image is hidden, rather than filtered through a polarized lens, allowing for higher resolution overall. But the active glasses are a sophisticated piece of technology, so they’re not necessarily inexpensive. One additional disadvantage is that active glasses aren’t cross compatible today, but manufacturers are moving quickly to develop a standard for all active televisions.

Passive glasses, because they have no machinery inside, are lighter in weight, less expensive and compatible with any other passive 3D system. As a result, they’re more likely to be included with a passive 3D television, although this can vary depending on the manufacturer. In many ways, they resemble the 3D glasses you’d see in most movie theaters. However, the 3D image you’ll see through them is often not up to the standard offered by active glasses. As well, because the 3D technology is primarily built into the passive TV and not in the glasses themselves (like active), the initial costs can be slightly higher.

Either way, if you’re worried which will fit over your prescription glasses, don’t fret. Both are designed to fit easily over corrective eyewear.

The answer is: No more expensive than an ordinary medium-to-high-end televisions, and the cost continues to drop. Why? Because companies are constantly inventing ways to produce hardware that makes 3D compatibility possible that doesn’t significantly increase the cost of production. So, 3D compatibility is just a new feature being added to many of the new HDTVs entering the market and, as is frequently the case with new features, they appear on the highest-end TVs first. This creates the mistaken impression that 3D television itself is expensive but, as with all new must-have technologies, an evolution towards 3D becoming a standard feature is inevitable, and we’ll see more and more companies embracing 3D technology across their television product lines in the near future.

As we’ve hinted, for all the reasons discussed above, there’s some variance in the cost of both sets and the glasses they use. Depending on the manufacturer, active glasses tend to be priced higher, but the television price points tend to be lower. Passive glasses that aren’t included with the television are cheaper, you’ll pay a bit more for the 3D technology built into the passive set.

Other than the sensation of experiencing in-home entertainment in a whole new way, the primary difference between watching 3D TV and the television you’ve been viewing all your life is simply wearing the  glasses. Right now, and for the foreseeable future, if you want to experience 3D TV, you must wear the glasses. Even so, it should be mentioned that there’s a small percentage of the population who, due to ocular disorders, are unable to perceive 3D even with glasses. This is called “stereo blindness” and affects somewhere between 2 and 12 percent of the population.

However, just to be clear, extensive research has failed to show in any way that 3D television causes eyestrain or other ocular disorders any more than watching traditional dimensional television.  Remember, all that 3D glasses are actually doing is filtering light. In fact, in the unlikely event that you do experience a problem while watching, it can actually be an effective early warning sign about a previously undetected eye condition.

Most 3D televisions deliver the optimum viewing experience when seen from directly in front. However, the best range for optimal viewing can vary from system to system, so it is best to test out 3D televisions before you purchase one.

By now you know that wearing 3D glasses won’t make images appear in 3D unless they’ve been transmitted in 3D. So, wearing your 3D glasses while you pause your entertainment and move around your house or check your laptop won’t change your perception of non-3D images anymore than wearing a conventional pair of sunglasses indoors.  But they will change the way you watch and experience television!