This past Sunday, I packed up my Sanyo Xacti pistol camera and headed over to a nearby Best Buy store. My goal was to re-run the same off-axis viewing tests that I conducted on a Sony Bravia 3D LCD TV at the CEA Line Shows. Except this time around, my guinea pigs would be Samsung and Panasonic products.
I picked a normal exposure for the correct (level) view and didn’t change it as I rotated the camera and glasses around. This was done so you could see any change in screen brightness.
First up was a Samsung 55-inch LED model. I settled in the comfy chair, pulled out the lone pair of active shutter glasses, and picked a few scenes from Monsters vs. Aliens.
Figure 1 shows a close-up view of the screen through the right eye lens, with the glasses positioned at the correct angle to the screen. No ghost images (crosstalk) were spotted and picture quality was high.
The next image shows the view with the glasses tilted about 30 degrees to the left. No objectionable ghosting here, either, although this particular scene is of a TV weatherman on a ‘flat’ picture tube – not much 3D going on here.
Figure 3 shows the view with the glasses tilted about 60 degrees to the left. The image is noticeably darker now, as the polarizers in the glasses are starting to cancel out the polarized light from the LCD TV screen.
Figure 4 shows – nothing! The glasses are tilted about 80 degrees to the left and the ‘twist’ of polarized light from the LCD screen is canceled out by the polarizing angle of the 3D glasses. Not surprising, considering that two polarizers are being used in the 3D glasses.
These tests don’t mean the Samsung glasses are completely free from ghost images when tilted. Figures 5a and 5b show two different views with the glasses tilted at about 45 degrees to either side, and you can see crosstalk in both images.
On to Panasonic! Figure 6 shows the 50-inch plasma screen head-on, as seen through the right lens.
The next figure shows the same screen with a tilt of about 45 degrees. Picture brightness has dropped a little, but there is no ghosting evident in the image.
Figure 8 shows the screen as seen at a nearly vertical angle, about 80 degrees. Image brightness is still good and there is only a hint of ghosting to be seen (look around St. Peter’s dome). Figure 9 shows the screen 90 degrees to horizontal and it’s still largely free of crosstalk.
From these tests. it should be pretty clear that plasma has a big advantage over LCD technology for viewing 3D, and that’s because plasma TVs don’t use polarizers as part of their imaging process. (Anti-glare glass is used, but doesn’t seem to have an adverse effect on 3D viewing angles.)
In contrast, it’s a tricky proposition to pair up polarized glasses with a polarized TV screen, as we’re just seen with Samsung and Sony LCD TVs. Your head really needs to be level to avoid seeing any ghost images.
It appears that the crosstalk problem is worse on Sony’s 3D LCD TVs because they’re only using one polarizer per glass lens (that’s the consensus educated guess). That decision results in images that are brighter, but are ridden with crosstalk – even when the glasses are positioned level to the screen. So there’s no allowance for head tilt – even slight amounts – with Sony’s approach.
By using two polarizers per lens, Samsung cuts down crosstalk more thoroughly, just at the cost of screen brightness. But you can tilt your head at a greater angle and not be distracted by crosstalk through the glasses.
Panasonic is also using dual polarizers and their images were about as bright as Samsung’s, but nearly free of ghost images when viewed at any angle. If and when OLED-based 3D TVs make it to market, you can expect to see that same level of performance.
So…now you know!
Posted by Pete Putman, June 28, 2010 7:00 AM
About Pete PutmanPeter Putman is the president of ROAM Consulting L.L.C. His company provides training, marketing communications, and product testing/development services to manufacturers, dealers, and end-users of displays, display interfaces, and related products.
Pete edits and publishes HDTVexpert.com, a Web blog focused on digital TV, HDTV, and display technologies. He is also a columnist for Pro AV magazine, the leading trade publication for commercial AV systems integrators.