Active 3D vs. Passive 3D
What are the differences in the TVs and Glasses? What are the Advantages and Disadvantages?
by Phil Conner and Robert Wiley
With LG, Vizio and Toshiba going with passive 3D glasses and Samsung, Sony, and Panasonic producing active 3D glasses and TVs, this battle is really heating up. Consumers are asking the questions, "when will I be able to watch 3D without glasses," and "what's the best way to watch 3D TV now?" Read on to find out.
Active vs. Passive debate is going to be a hot debate amonst television manufacturers and consumers in 2011 and beyond.
Passive 3D Glasses
Passive 3D glasses are any 3D glasses that don't require a power source to view 3D content. The two major types of passive glasses are anaglyph and polarized 3D glasses. One of the main benefits to passive 3D glasses is cost. Since they do not require a power source or powered lenses, passive 3D glasses can be very inexpensive. Anaglyph glasses, commonly seen with one red and one cyan lens, are often seen made out of cardboard with cellophane lenses. Though anaglyph glasses do show the viewer a 3D image it is the least advanced of all methods of delivering 3D and because they use color to separate the images some or all color information is lost to the viewer.
Polarized 3D glasses come in two forms, linear polarized and circular polarized. Linear polarized glasses require the use to maintain a vertical head position, tilting your head left or right can break the 3D effect because the content relies on one eye seeing the vertically polarized image and the second eye seeing the horizontally polarized image. When the head is tilted the polarized lenses no longer line with the polarized double image on the screen. Circular polarization does away with this problem but it requires a special projector and filter and will not be used on 3D televisions.
Another benefit to passive 3D glasses is that since the viewer is being shown both images at once it does not half the frame rate of the content like active glasses do.
Active 3D Glasses
Active 3D glasses require a power source to power the lenses in the glasses, for shutter glasses a mechanism to sync the glasses to the display is also required. Head mounted displays are considered active 3D glasses but since they contain a pair of displays built into the device they are not relevant to this discussion.
Shutter glasses are the active 3D glasses most viewers will use for 3D content, they use LCD lenses that are commanded to alternately open and shut each lens to show each eye a different image. It used to be that shutter glasses were connected by a wire that provided both synchronization and power but now most shutter glasses are powered by small batteries and receive sync signals via an infrared beam similar to a TV remote. The technology involved makes shutter glasses considerably more expensive than passive glasses, expect to pay anywhere from $50 to $100 for a pair of shutter glasses. Most new 3D TVs will include one pair of glasses but additional pairs must be purchased separately.
The major disadvantage to active 3D glasses is that the separate images for each eye are not delivered at the same time. The content will alternate the images shown to each eye at whatever the frame rate of the content and refresh rate of the display offers. For example, with 60 frame per second content each eye is being shown only 30 images per second effectively halfing the frame rate seen by the viewer. This is most noticeable during slow camera pans or during fast motion. The higher the frame rate the smoother each of these actions will appear so active 3D glasses can show slight to noticeable judder effects during these scenes.
Active 3D glasses allow full color and picture information since both images are not being overlayed on one another and we feel that this benefit outweighs the effect that active glasses have on frame rate. Until 3D without glasses is commonplace shutter glasses should provide the best home 3D experience. For more information on 3D glasses and how they work see our 3D Glasses - Active and Passive, Polarized, Shutter and Color Anaglyph 3D Glasses article.
Samsung's Plasma and LCD/LED televisions use active shutter glasses to display 3D.
Advantages and disadvantages of Both
Which one of these competing technologies will win out and what are the advantages to each? Active 3D requires more expensive shutter glasses and the extra emitter in the TV so costs will normally be higher for this technology. With active 3D, viewers are able to see full 1080p to each eye if the inbuilt TV technology allows for it. Typically in the past most all plasma 3D Active TVs have allowed for 1080p to each eye. LED-LCDs are just getting there in 2011. Seeing the higher resolution to each theoretically produces deeper 3D images and higher picture quality. One other disadvantage of active 3D viewing is that it can tire the eyes giving us eye fatigue, or worse for some – a headache.
With passive 3D, the viewer will see 540 lines of resolution to each eye, or half 1080p (provided the source is 1080p). So, theoretically the picture will have less depth and quality than one of 1080p. The advantages of passive 3D is that the glasses are much less expensive and need no power. 3D glasses of this variety can cost as little as $5 a pair and often come with the TV, so setting the family up for some 3D viewing will not hit the wallet as hard. Passive 3D viewing will not cause the eye strain and fatigue that active 3D will since the glasses are not actively opening and closing.
LG's 3D LED/LCD televisions use passive 3D while their plasmas still use active 3D.
Our Viewing Experience with Both
From our experience last year with active 3D, we noted lots of annoying flashing in the glasses at times due seemingly to confusion with in-room ambient light. The other problem we noted consistently was blurring in the bottom corners of images. This year, we do not see these problems from the 3 or 4 active 3D TVs we have reviewed. The glasses and TVs seem very much improved and have for the most part eliminated these deficiencies leaving us with an extremely involved experience and tons of 3D picture depth. The eye strain and fatigue we experienced last year also seems greatly reduced.
Though high end passive 3D viewing is new to this year, we have been pleasantly impressed. The main objective of 3-dimensional viewing is to involve and engage the viewer on a more intricate level and passive 3D certainly accomplishes that – depending more or less upon the source material. Watch for new reviews that we'll be conducting with more passive 3D experimentation and commentary.
Sony is also sticking with active 3D in all their 3D enabled models.
The Debate Heats Up
Recently, the debate between active and passive 3D is getting hotter due to the choices of manufacturers to produce one or the other technology. LG and Vizio are producing only passive 3D in their LED-LCD TV lineups. Panasonic, Samsung and Sony are producing active 3D only in their lineups. Toshiba is producing both active and passive 3D and also trying to bring to market the first 3D TVs without glasses. It will be interesting to see if the lower overall price point of passive 3D offerings forces the hand of the active 3D manufacturers.