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Published: 2010-07-25 - 15:38:04
Home Theater : Ask The Expert

Can My Plasma or 120 Hz LCD HDTV Be Upgraded to a 3D TV?

By Chris Boylan

Although the question below came via our forum and is specific to a plasma HDTV, we've gotten similar questions from readers about the ability to upgrade existing LCD or LED TVs to support 3D capabilities.  Our answer covers all three TV technologies.

Question:

Dear Big Picture Big Sound,

As I have read about how 3D images are produced through alternating two image sources simultaneously with the requirement of the display having a refresh rate quick enough to produce the 3D images, I was wondering if it might be possible for a normal plasma HDTV with a refresh rate sufficient to handle the 3D image data, to produce 3D Images?

Or alternatively, could an aftermarket 3D Kit, such as an emitter, be connected to the TV or player set so as to enjoy 3D images despite just using a normal 2D HDTV?

I'm kind of hoping there's a possibility of the above happening so I could enjoy 3D TV without investing in a whole new television.

Thanks,

-Vinnythecent


Answer:

Hello, Vinny,

Unfortunately what you're hoping to do can't really be accomplished using a non-3D-compatible TV.  It's not technically impossible for some third party vendor to create a solution, but the motion and flicker artifacts would be so bad as to make the image virtually unwatchable.  So I find it extremely unlikely that anyone is going to come to market with a solution for this.

It's not just the screen refresh rate of the TV that matters (although yes, the TVs do need to be able to refresh the image at a rate of at least 120 Hz in order to produce the left/right 60 Hz rate used by current active shutter 3D glasses), but it's the TV's input capabilities that matter, as well as what the TV does internally with that input signal.

Non-3D plasma TVs are out of the running from the get-go because they can't refresh at 120 Hz.  The so-called "subfield drive" that is used in plasma TVs, and that has a rating of 480 Hz or 600 Hz, is not the same thing as a full screen refresh rate.  The sub-field drive is the technology used to build the image.  A frame on a plasma TV with a 600 Hz sub-field drive is built out of ten sub-frames, so the screen flashes ten times for each individual frame.  But the full screen image itself is only refreshed 60 times per second (60 Hz).

There are exceptions to this, of course.  Some Pioneer, Samsung and Panasonic plasma TVs have a Cinematic Playback mode (24p native mode) which flashes the screen two, three or four times for a 24 frame/second input source.  This processing results in a 48 Hz, 72 Hz or 96 Hz refresh rate, but again, this doesn't help you from a 3D perspective because the only input supported for these modes is standard 1080p/24 - not the augmented 1080p/24 frame-packed output from a Blu-ray 3D player.

Moving onto the "top-bottom" and "side by side" formats used for 3D signals in broadcast TV, you'll have a slightly different problem.  For compatibility purposes, these signals do use a standard 720p, 1080i or 1080p broadcast format, but they split the screen in half, with the left and right images either next to each other or stacked one above the other.  Your TV could display this, but it would just look like two nearly identical images next to or on top of each other on the screen.  Your TV doesn't have the necessary processing to isolate and expand these half-frames into two distinct full screen frames, each of which would be alternated on the screen at 60 Hz for a total display refresh rate of 120 Hz.

Side by Side 3D
Unless your TV is 3D-ready and compatible with side-by-side 3D broadcasts, this is what the new 3D channels will look like on your TV. (sample 3D side-by-side image from wikipedia)

For a non-3D LCD or LED TV, the prospects of displaying 3D are no better than plasma, again due to the input capabilities of the TV.  If an LCD or LED TV could accept a 120 Hz input, and just display this as is, then it would be possible for some manufacturer to create a sort of converter box that would convert all of the available 3D formats (frame-packing, top/bottom, side-by-side) into a 1080p/120 Hz signal, and use an external emitter synchronized with glasses.  But since all non-3D LCD and LED/LCD TVs are limited to a maximum of 1080p/60Hz input, any potential outboard solution (which, again, does not currently exist and probably never will) would be riddled with motion artifacts.

Converting a 3D image into something that would work with existing LED or LCD TVs would mean chopping out half the frames: 60 frames/second x 2 would have to be converted to 30 frames for the left eye and 30 frames for the right eye for a total frame rate of 60 Hz.  This reduction of image data would result in choppy, unnatural-looking motion.  Yes, some third party could conceivably create an emitter that would synchronize with this signal, but it would look pretty bad from a motion standpoint.  And I don't think any company is going to want to create such an inherently flawed solution (nor would consumers be happy to own it).

Also, a secondary (but still important) issue is that the new 3D-capable Full HD TVs from Samsung, Panasonic, Sony, etc., have been specifically designed to support 3D signals.  The underlying technology that is used to create the image has been enhanced to prevent crosstalk (the bleed of left images to right eye and vice versa).  For plasma TVs, this means a faster-switching phosphor.  For LCD TVs it means a faster panel response time.  These same enhancements actually make these TVs look better than last year's models even when watching standard 2D content.

Really the only TVs made prior to 2010 that are 3D-compatible are the 3D-ready TVs made by Samsung and Mitsubishi since about 2007.  Samsung and Mitsubishi both made 3D-ready DLP TVs and Samsung even made some 3D-ready plasma TVs (but none were 1080p models).  These use a checkerboard format which effectively splits the resolution between left and right eyes, and an emitter to synch with compatible active LCD shutter glasses, or you can use 3D glasses with "DLP Link" technology to eliminate the need for an outboard emitter.  For Mitsubishi, they've created a set-top box that converts all of the available 3D formats to the checkerboard format.  For those older Samsung TVs, you can use a computer as the 3D source, or you can use the new Panasonic DMP-BDT350 Blu-ray 3D player as the source, as it has a checkerboard output option.  You would need to have the compatible 3rd party outboard emitter and 3D glasses for the Samsung plasma TV though, and I believe these may be out of production.

Unfortunately for those who recently bought a nice non-3D TV, there will be no 3rd party aftermarket solutions to turn them into 3D-ready TVs.  My recommendation for people buying high-end HDTVs today is to get one with 3D capabilities otherwise buyer's remorse may set in, in the not so distant future.

Regards,

-Chris

Keep those cards and letters coming! if you have a question for one of our home theater experts, shoot us an e-mail to "Ask The Expert." We'll select among these for future installments in this column. Due to the volume of requests we receive, we cannot reply to each question personally.

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