 Picture Quality: What makes a picture great!Educate yourself with easy to understand details: picture quality; contrast; color; adjustments; resolution; aspect ratioPicture QUALITY
Contrast:Contrast is the difference from lightest to darkest shown on your display. The higher the CONTRAST RATIO, the wider the range, and more detail you’ll see, typically in the darker or brighter scenes. In a bright room, you won’t see the detail you’ll notice in a darker room, as the screen will wash out some due to the ambient light.You can’t necessarily tell in the stores, because many of the sets are misadjusted. Read on. Make the leap of faith – either trust your eyes at a store (risky behavior) or trust specs from the manufacturer. Get it in writing. You’ll never be able to prove them right or wrong, but it will give you some confort.
Color:Don’t worry about it. ALL the display technologies can do color really, really well. If I was to buy a DLP, though, I think I’d go with a 7 segment (or more) color wheel, because they may be an advantage to that.
Adjustments:All the electronics manufacturers have fancy names for their picture ‘enhancement’ circuits. Surprise: not all enhancements look better than without. It’s a matter of personal taste AND what you are trying to correct. Sometimes the lesser of two evils is what you’ll find. Most enhancements can be turned off. Take enhancements wit a grain of salt and be happy if they make you feel like something improves when you try them.You can get a certified technician to come to your home and calibrate your TV.
Antenna Hint:In digital TV, you get all or nothing. You can’t improve a picture with more signal strength.You will notice that on some HD TVs, SD picture look blurry, with pasty skin tones, like the newscaster has a wax face. This is a consequence of the change in the bandwidth between recording and playback. Although the bandwidth of SD is said to be 5 MHz, it is not a sharp cutoff, is more gradual. The roll-off starts before 5 MHz (don’t ask – keep reading), but some image information above 5 MHz survives the recording process, but mixed with electrical noise (snow). The broadcaster has to decide if he wants to filter it out. If the broadcaster decides to filter out the snow, to bring you a sharper picture, some image information is lost also, resulting in increased blurriness. More… is actually less. Some people would prefer the snow to the blurriness, but others might not.
Picture RESOLUTION:Resolution = detail! Below we break it out by display technology.
CRTVideo Bandwidth determines analog resolution. Bandwidth is frequency response. There’s little wiggle room here – you get what you get. As CRT is at the peak of its development, unless you buy junk, your TV should be able to excel.
LCD, PLASMA, DLPThe higher the resolution, the more picture elements (Pixels) on the screen. This is especially important as screen size expands. Here’s where specsmanship can drive you crazy. Commonly quoted resolutions are followed by a lower case p or an i.Progressive scan, paints the picture top to bottom, all at once. 60 frames a second. The term ”interlacing” refers to the practice of drawing all of the odd numbered lines on the CRT, and then drawing all of the even numbered lines, which are drawn interspersed with the odd numbered lines. For 1080i, the 540 odd numbered lines are one “field”, and the 540 even numbered lines are the other “field”. Drawing 60 fields per second will prevent flicker on a CRT TV. A disadvantage of interlacing is that, with only 30 full frames (2 fields = one frame) per second, it doesn’t portray motion as smoothly. Another disadvantage is that data compression is not as efficient. So, here it comes. I hate to give you this, but only because I don’t think it means much to most people and it can be made very confusing. Still, in an effort to give you detail you might wish…
480i is what you are used to on old standard TV – called “NTSC”480p is possible on your progressive scan DVD player, twice as good as standard TV. 720p is 1280x720 pixels progressive – called Hi-Def 1080i is 1920x1080 pixels interlaced – called Hi-Def 1080p is 1920x1080 pixels progressive. Called Hi-Def- Expensive (at first) sets are moving to this resolution quickly, not that it’ll be broadcast. But you will be able to see it on HD-DVD players. And Beyond. Yes, there are more to come, with higher resolution. (In prototype already - 4x 1080p!)
WHAT SHOULD YOU DO?Don’t worry about it. Seriously. The real issue today is what will be broadcast and you have no control over that. Video compression and conversion involve massive computing power and this is where the picture is degraded most.How did this happen? Well, I wondered about that too. 1080i and 720p require about the same bandwidth when showing live action: A 1080i image has twice as many pixels, while 720p shows twice as many frames per second. While showing films - which are shot at 24 frames per second, 720p requires about half the bandwidth of 1080i. Tastes great – less filling. Some say 720p is better for sporting events, (and Panasonic underwrote ABCs Monday Night Football to get 720p out there in the real world!) while 1080i looks better for documentaries, dramas, and anything that comes in at film’s 24 frames per second. Unfortunately the networks are picking one format for all their shows. ABC and ESPN have chosen 720p. FOX has chosen 480p but will switch to 720p in the future. All other networks are using 1080i.
Why is this so confusing?
Oh, it’s even worse.Native resolutions (read that as what the displays actually do) may vary from that above. (Then what happens?) They convert to one of the above, some doing a better job than others.
No, it’s even MORE confusing.For instance, wobulation. Here’s a technique where the picture is wobbled slightly to give the effect of more resolution. It works - is all you need to know. No, you can’t tell it wobbles.
Or more confusing still.The shape of the pixel can be made so the space between them isn’t as wide.And then you get your brand spankin’ new TV back to the Home Theater you are putting together then ask yourself: Is this picture 1080i or 720p or 480p? This can be hard to tell. When a TV station decides to provide an HD sub-channel (That means along with its standard analog channel), that sub-channel is normally 1080i (or 720p) all the time at the transmitter, even if some (or most) of the programming originates at NTSC (older, ‘old standard’ tv) cameras. There is no technical requirement for this, but it seems to be nearly universal practice. Thus your receiver’s “HD detector” is not a reliable indicator of whether the program is actually HD. NTSC (‘old style’) 4:3 images will have black bars on the side that you probably cannot eliminate because they are part of the 16:9 transmitted image. The best way to determine if you are REALLY seeing HighDef:If the image is 16:9 and it is not stretched and there are no black bars on the sides and nothing is clipped off the top or bottom, then the image is 720p (ABC and ESPN) or 1080i (everyone else). FOX is the only network that violates this rule-of-thumb. ESPN expands all StandardDef material to 16:9 through a combination of stretching and clipping. Only ESPN does that. Did you just notice that the networks didn’t all feed at the same trough? Correct. Why? Some feel one is better, some feel the other is.Confused? Time for a nice iced adult beverage.
ASPECT RATIO:Ah, you do need to get a handle on this. What you grew up with was a 4 to 3 or 4:3 (width to height) picture. That’s going away soon. Soon it will be 16 wide by 9 high (16:9). More like a movie screen. 16:9 is called WIDESCREEN. HDTV is 16:9. But some films are even wider than that, so you see everything, but there are then bars above and below the picture. Similarly, you can watch a 4:3 picture on a 16:9 set and see bars to the sides of the picture.Manufacturers have ways to deal with this: STRETCH the image. Zoom in. Lose some of the sides. Generally, your HDTV display will come with at least several choices. Remember, if you watch on a PLASMA or CRT, you may burn in those bars since some display devices will, over time, produce a ‘memory effect’ of those things that stay on the screen for long periods.
WHAT SHOULD YOU DO?There’s little you can do. You are stuck with what they give you. You’ll get used to it. Copyright © 2005, 2006 www.GreatHomeTheater.com | Home Theater Made Easy | Home Theater guides and reviews | picture quality
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