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Study finds passive 3D TVs superior to active

A study by the author of the well-respected DisplayMate calibration software, pitting active 3D TVs against passive ones, finds passive models better in most aspects of picture quality.

Passive 3D TVs come with up to 4 pairs of inexpensive glasses, but a new shoot-out says active 3D TVs, which use expensive shutter glasses, perform worse. Sarah Tew/CNET

A new study comparing the two current types of 3D TVs available for sale, active and passive, finds that passive 3D TVs had superior image quality to their active counterparts. I was personally surprised by the finding, since I've found the opposite in my reviews comparing the two types of 3D TVs.

The author of the study, Raymond Soneira, is the man behind the DisplayMate evaluation and calibration software. I've found his past work generally on target and well-researched, with plenty of supporting labs-based observations. This study, encapsulated in an article called 3D TV Display Technology Shoot-Out, is in the same vein.

If you're at all interested in 3D TV or 3D imaging in general, the entire article is worth a read. Here's the main conclusion:

Based on our extensive lab measurements and visual test comparisons between 3D TVs with FPR Passive Glasses versus 3D TVs with Active Shutter Glasses, we found that the Passive Glasses TVs delivered substantially and demonstrably better all around 3D imaging, 3D Contrast and sense of 3D depth, better 3D sharpness, better overall 3D picture quality, immersion and realism, and freedom from 3D ghosting, image Crosstalk, and flicker. This was true in all but a small number of situations, all of which we document [in the report].

From the passive camp Soneira tested an LG 47LW6500 and a Vizio E3D470VX, while from the active camp he chose a Samsung UN46D7000 and a Sony KDL-46HX729. All are LCDs, and all but the Vizio use LED backlights. He did not test any plasma TVs but writes that "they all use Active Shutter Glasses that are virtually identical to the LCD models, so our conclusions regarding their flicker, comfort, convenience, and cost apply to them as well."

The meat of the article is devoted to breaking down the observations and measurements of the various 3D picture quality factors, among them image brightness, flicker, crosstalk/ghosting (both straight on and from various viewing angles, positions, and head tilts), resolution, and sharpness. In every category Soneira found passive superior to active, and he backs up his findings extensively with lab tests, charts, and precise descriptions of program material complete with time stamps. The idea is that interested parties can check the shoot-out's findings for themselves.

My reactions
I haven't reviewed any of the exact TVs used in the shoot-out, but I've seen and written enough about both kinds of 3D to have formed the general conclusion that I like active better.

At this point it's worth stressing again that my experience with 3D TV is not based on any measurements or lab tests; for all of my 3D evaluations to date I've simply sat down in front of a comparison lineup and watched select sections of 3D material, mostly from Blu-ray, and written about the differences I saw.

I do agree with many of the shoot-out's findings; namely that passive 3D TVs can get brighter, crosstalk/ghosting is less visible than on most active 3D TVs, and the passive glasses are more comfortable to wear and much more conducive to performing non-TV activities. For these reasons alone many people will prefer passive.

Among the passive 3D TVs I've reviewed--the Vizio XVT3D650SV, LG 47LW5600, and Toshiba 47TL515U--my main complaint has been the incidence of jagged-edge artifacts. Here's a quote from my review of the LG LW5600, regarding watching the "Tron: Legacy" 3D Blu-ray:

In many scenes we could see jagged edges along visible lines, for example along the edge of Gem's outfit, the back of the receding girl's suit and the lit circle in the distance (28:11), or the diagonal lines on the floor of the arena (39:04). The effect was worse and more distracting when movement caused the jagged edges to crawl, as they did during a quick pan over the glowing Frisbee fight (33:40) and the arena (42:04) for example. Moiré artifacts were also relatively common, for example in the crawling lines of Alan's tie in Chapter 3 (16:30) and the patterned floor in Chapter 5 (28:22).

The DisplayMate article, on the other hand, says, "jagged line artifacts are barely noticeable unless you are searching for them." Some amount of TV reviewing does involve searching for artifacts (think of us reviewers as archaeologists!) but I noticed these jagged edges the first time I saw passive 3D TV in action, at the Vizio booth at CES, and I find it difficult to un-see them.

The article also says (correctly) that active 3D glasses flicker, and the author says flicker is one reason why he has previously shunned 3D TV. In my experience the flicker of active 3D glasses is generally not noticeable unless I'm under a bright fluorescent light source. Different people have different thresholds of perception for flicker, as the article points out, and for me the flicker of active glasses hasn't been an issue.

That said, I still haven't logged as much 3D viewing time as I'd like, and I have experienced some fatigue after watching a lot of 3D. Until now I've always attributed it to bad 3D content or less-than-ideal viewing conditions, but perhaps what the article calls "subliminal flicker" is a culprit. I just don't know.

A good many of the other arguments have to do with resolution and apparent sharpness, which is the major beef between the two camps. Basically, the passive camp says its technology, called film pattern retarder (FPR), provides full 1080p resolution despite the fact that only half of those horizontal lines (540) reach each eye. The fusing of the two 540 halves happens in the brain, the article explains, and according to Soneira's tests the result is full 1080p detail.

The active camp touts the ability of its TVs to deliver "1080p to both eyes," in a process that doesn't rely on the brain fusing two half-resolution images. One of the principal advocates for active 3D is Joe Kane, another author of display calibration and evaluation software; see his Web site and a demo he did for Home Theater magazine for that side of the story.

I haven't done the tests in the DisplayMate 3D shoot-out myself (yet) but suffice it to say I've seen 3D looking somewhat softer on a passive TV than on an active one. Not "half" as sharp, as the numbers above might indicate, but still discernably less sharp. In my own early comparison (again, based purely on subjective observation), a colleague and I found the passive Vizio softer than the active Panasonic with the same sources from a seating distance as far as 12 feet from 65-inch sets.

The difference in sharpness definitely decreased as we moved farther back, and at a certain point (as with all resolution differences) it's not discernable. I also noticed very little difference in resolution when watching a 47-inch passive LG from 7 feet away, although again it looked a bit softer subjectively when compared (after switching glasses back and forth) with active models. I did, however, notice visible horizontal line structure from that distance, something the article says shouldn't be possible.

The article also makes the point that crosstalk on active models dulls their apparent resolution advantage. I can certainly see the logic in that, but I've also seen that many active TVs (like the Samsung UN55D8000, the Sony XBR-HX929, and most 2011 plasmas) have very little apparent crosstalk.

Both of the active TVs in the shoot-out may have more or less crosstalk than others I've reviewed; it's tough to tell, and crosstalk varies significantly with different models in my experience. That's one reason why I'd have liked to see the shoot-out include at least one plasma TV, or even one of the flagship LED models I tested.

After reading the report I had a healthier respect for passive 3D than I had before, but it didn't change my mind. I don't think that will happen until they can figure out a way to get rid of those jaggies.

Your takeaway
If you've read this far in this post, and especially if you've also read Soneira's shoot-out all the way through, it's safe to assume a) you actually care about 3D TV picture quality and b) you'll be hearing a lot more about active versus passive in the near and distant future. For you, concerned reader, my advice is pretty lame: see for yourself. Check out both versions at a store or preferably at someone's home, armed with knowledge about their strengths and weaknesses. If you're overly bothered by any one problem, then your choice is easy.

My hunch is that most TV shoppers simply don't care enough right now about 3D, let alone passive versus active, to make the differences a major factor in their buying decisions. Do you? Let me know what you think in comments.