Passive 3D TVs are the alleged wave of the future. Passive 3D TVs, as you’ve heard, don’t require the clunky, battery-powered active 3D TV glasses. Instead of the weighty active 3D TV glasses that you have to wear to watch active 3D TV content, passive 3d TVs let you wear the lightweight, comfortable non-electronic glasses that you’ve probably worn at an IMAX theater. Furthermore, passive 3D glasses don’t produce the “flicker” effect that you see when wearing active 3D glasses and looking at light sources other than the 3D TV.

But there are some important things you should know about passive 3D TVs. In spite of the benefits in terms of comfort and the “flicker free” claims of passive 3D glasses, the most glaring downside of passive 3D TV is that it produces literally half of the resolution of active 3D TVs. That’s because the way passive 3D TVs work is by sending half of the lines of content to one eye and the other half of the lines to the other eye. So, if you have a 1080 resolution, then each eye would be getting 540 lines each. As such, you get a lot of the artifacts and picture quality issues that you see with a 1080i (interlaced) picture. You’ll see lines and occasionally “jaggies.” You’ll also see some softness in the picture.

This issue is worsened by 3D TV content that comes via broadcast, cable or satellite channels. The way that these mediums deliver 3D content is fundamentally different than the way Blu-ray discs show 3D content. The details are a bit complex, but what matters to you is that 3D content from a cable, satellite or broadcast provider won’t be full HD. And if you are wearing passive 3D glasses, the vertical resolution gets halved after that. If you have a resolution of 720p for your 3D content and you’re using a passive TV, then your content would effectively be even lower resolution than VHS.

That being said, passive 3D technology is improving. For example, LG has been applying a special layer to their passive 3D TV screens that reduces cross-talk. Cross-talk is when remnants of both images are visible, rather than having them combined to complete the stereoscopic illusion. This is also called ghosting. This film over the passive 3D TV screen also brightens the picture. Some prominent reviewers have claimed that high end passive 3D TV screens are brighter than some of the best active 3D TV screens. Also, once cable and satellite providers begin providing higher quality content, much of the negative aspects of passive 3D technology will be offset.

All of these developments in 3D technology reinforce the notion that it might be a good idea to wait before investing in a 3D TV. Today’s latest and greatest may be tomorrow’s annoying relic, with a legacy issue that has been long fixed by a new improvement. Much of the improvement can be done on the content side, but you should still be careful when buying 3D TV equipment.