The View from the Floor

By Scott Wilkinson • Posted: Jun 2, 2008

My wife Joanna was on a business trip last week, and she found herself in a hotel room with an LCD TV. As she was doing her daily stretching routine on the floor, she turned on the TV and noticed that the colors looked very weird from that angle, "almost like a color negative" as she wrote in an e-mail. "What's up with that?" she wondered.

Joanna had stumbled onto one Achilles' heel of LCD TVs—color shifting when viewed from far off axis. Of course, some LCDs are better at this than others, and the hotel undoubtedly bought the cheapest TVs available, which are certain to exhibit more color shifting than higher-end models. I saw the same thing on my recent trip to Japan—the personal LCD screens at each seat on the airplane looked just like a color negative beyond a certain angle as I walked by.

This got me thinking about the differences between LCD and plasma flat panels, which is one of the most common questions I get from readers and friends. So let's go over it step by step.

LCD Advantages: High brightness works well in environments with ambient light; screen reflections are diffuse, thus not as distracting as plasma screen reflections—again, good for rooms with ambient-light sources; no danger of image retention or "burn-in" from static images; 1920x1080 resolution more common in smaller screen sizes; generally consumes less power than plasma.

LCD Disadvantages: Off-axis color shifting and contrast reduction; black levels can be higher than plasma, especially with low-end sets—this does not apply to LED-backlit models; objects in motion often lose a lot of detail (except on sets with well-implemented 120Hz frame interpolation); large screen sizes generally more expensive than comparably sized plasma.

Plasma Advantages: No off-axis color shifting or contrast reduction; generally lower black levels and better shadow detail than LCD; generally less expensive than comparably sized LCD; motion detail generally sharper than LCD.

Plasma Disadvantages: Potential for image retention or "burn-in" (though this is much less of an issue in modern sets compared with early-generation models); generally not as bright as LCD, so plasma doesn't work as well in environments with lots of ambient light; screen reflections are generally sharp and well-defined, thus more distracting than LCD; 1920x1080 resolution less common than LCD; generally consumes more power than LCD; APL (average picture level) limiting causes bright objects to appear brighter in dark scenes and less bright in bright scenes.

Bottom Line: If you are primarily interested in watching movies in a light-controlled room, especially if some viewers will be off axis, I think plasma is the better choice, though I generally recommend a model with 1920x1080 resolution to avoid any possibility of scaling artifacts. On the other hand, if you want to watch TV in a well-lit room, LCD is the way to go, though the image on a cheap one might look like a color negative to anyone stretching on the floor.

If you have an audio/video question for me, please send it to scott.wilkinson@sourceinterlink.com.

Comments

Submitted by Dave on June 4, 2008 - 4:08am.

Any chance your two comrades will ever update their blog postings?

Submitted by Scott Wilkinson on June 4, 2008 - 11:08am.

Good question! They are on their own in that regard, but I will certainly pass your question on to them.

Submitted by Mike on June 4, 2008 - 4:09pm.

So, what is the technical reason for the color negative effect on LCDs? Would the same effect be seen on DLPs or other rear projection devices?

Submitted by David Vaughn on June 4, 2008 - 9:40pm.

Scott, Great blog as usual! I'm still trying to decide what to get for the "kid's room" (play room) for video games and the kids shows. Low price is screaming out to me, but the quality side of me says get the best for them. What to do???? David

Submitted by Dave on June 5, 2008 - 7:07am.

Make sure you read the warranty completely for 2nd tier and below LCDs TVs. Many can not be repaired after the warranty expires or requires you to ship the unit to the repair center for repair costing you big bucks often the difference is cost between a tier one and a second or third tier TV. Some of these TVs do not have repalcement parts available. 2nd or third tier Insignia, Vizio, Westinghouse etc.

Submitted by Scott Wilkinson on June 5, 2008 - 1:26pm.

Mike, the color-negative effect and reduced contrast when viewing LCD TVs off-axis is mainly due to the quality of the polarizer. LCD TVs have a backlight behind the LCD panel, and that light must be polarized before it passes through the panel, because the pixels let more or less light pass through by changing their polarization. Light waves can vibrate in any direction; polarization causes them to vibrate in the same direction. If they hit a pixel with the same polarization, they pass through; if they hit a pixel with a different polarization, less of the light gets through. The amount of light that gets through depends on the relationship between the light's polarization and the LCD pixel's polarization. Low-quality polarizers can cause the light coming out of the TV to shift colors and lose contrast.

Submitted by Fred on June 5, 2008 - 4:06pm.

What are you doing reading Scott's blog, when MINE is finally up!

Submitted by Scott Wilkinson on June 6, 2008 - 10:09am.

Sorry, that last sentence was incomplete. Low-quality polarizers can cause the light coming out of the TV to shift colors and lose contrast when viewed from off-axis.

Submitted by tom norton on June 6, 2008 - 9:39pm.

Scott: To your comment that LCDs with LED backlighting have good blacks, I would add that this only applies if the LED backlit set has local dimming, which can selectively darken portions of the image as required by the source. There have been LED backlit LCD sets without local dimming, but I'm not aware of any at present. There's only one manufacturer currently making LCD sets with local dimming (Samsung) but we expect to see them from other sources before long. _

Submitted by Scott Wilkinson on June 7, 2008 - 5:04pm.

You are correct, local dimming is the key to good blacks. But you are also correct that there are no currently available LED-backlit LCD TVs that do not use local dimming, which is why I didn't mention it. (Probably should have, though.) In addition to Samsung, SIM2 is working on such an LCD TV based on the Dolby HDR (high dynamic range) technology, and I think other manufacturers are also working on implementing this idea.