Sunday, September 9, 2012

Picking out a TV

A friend of mine is wanting to buy a new TV set but doesn't know what to really look for when judging picture clarity differences.  Most people jump into a car and drive over to their favorite big box store or electronics salon and compare images from the myriad number of sets hanging prominently from the wall.  Such sales displays are all driven from a video distribution system with little or no chance to evaluate anything since manufacturers push the color levels to unreasonable limits to create the best possible WOW-effect.  So how can you tell? Here are a few tips that with even such limited test signals you can see visual differences.

Unless you have a trained eye, it is difficult to see more than color balance differences in sets. Hooking up a dedicated BluRay player, a good HDMI cable, and a good movie source is the best way to evaluate a set, but most showrooms cannot accommodate such a request. So you must look for differences in the signals simultaneously delivered through their video signal distribution system that CAN tell you something about the set.

Most people are familiar with what is called JPG noise in digital pictures, an artifact of a compression and decompression process that leaves speckles in a picture.  In HDTV, this video noise appears along the outer perimeter of objects. More easily seen in slow moving things like people walking against high-contrasts backgrounds, a video noise appears highly visible on cheap sets and less to invisible on better sets. Look for this noise and you will quickly sift out the sheep from the goats. Lower speckles means a clearer picture.

Look at the hair clarity on the RH dancer or belly speckles on the LH dancer to see the effects of video noise
If you like action and motion, you must look for fast screen refresh rates of at least 240Hz in LCD TVs (the Sony Bravia KDL-46HX929 has a 900Hz refresh rate). While most taped broadcasts are 60Hz, live events will produce more life-like realism with less motion blurring. An NFL football pass or a golf ball soaring through the air is a good test for motion blurring. If you buy a 3-D TV, buy at least a 240Hz model since in 3-D mode the refresh rate is actually 1/2 that specified (one frame scan for your left eye and one for your right means half the specified rate).

Black (or contrast level) is another test you can see pretty easily in such an environment although it is best detected in a darker room.  When the picture drops out such as a moment between commercials or in a really dark night scene, marginal black representations appear gray. Overly black situations will not show enough detail in darker images or even create weird colors in the shadow or black areas.  The center image below shows good black levels while the L image shows too little and the R image is overly black.

Do not be too quick to judge color accuracy and black levels since all sets are calibrated from the manufacturer to give the most wow but not the best color and black level. Buy a test DVD, such as the Digital Video Essentials "HD Basics," and once you narrow down a set, ask the salesperson if you can reset the display settings from its instructions. It takes a few minutes but the results may surprise you as to what a well-respected brand name set can and cannot do.

All sets are compromises but as mentioned Plasma sets tend to find their ways into more demanding homes. The only issue with Plasma is that such sets run pretty hot compared to the others (LCD/LED) and will put an additional load on your home A/C.  I have measured as much as s 20 degree F screen temperature difference between models using a hand-held infrared thermometer. This is a parasitic cost of operation that like a tube amp and preamp you just live with if you like what you see.
Whatever TV set you end up getting, use good interconnect cables just as you would for your audio system. Plug the TV into the same power conditioner as your system to minimize noise and ground-loop effects.

Yours for higher fidelity,
Philip Rastocny

I do not use ads in this blog to help support my efforts. If you like what you are reading, please remember to reciprocate, My newest title is called Where, oh Where did the Star of Bethlehem Go? It’s an astronomer’s look at what this celestial object may have been, who the "Wise Men" were, and where they came from. Written in an investigative journalism style, it targets one star that has never been considered before and builds a solid case for its candidacy.

My other titles include:
Copyright © 2015 by Philip Rastocny. All rights reserved.

No comments:

Post a Comment

To comment on this blog, you must first be a member. All comments are moderated.

Note: Only a member of this blog may post a comment.