Why does standard definition TV tend to look so terrible on an HDTV?

[ericl]

Standard definition TV programming has a tendency to look bad on HDTVs, but why? What is it that causes this? Is it the HDTV revealing deficiencies in the signal? or is it some wacky processing on the HDTV? Some standard def stations can look OK, such as HBO stations, but generally, any SD content on my HDTV is far inferior to that on 2001 model Panasonic 27" sdtv. What's going on here?

[Smokey]

My guess is most HDTVs (especially on fixed-pixel displays) tend to upconvert SD signal (640 × 480) to HD (1280 × 720, 1920 × 1080).
And unless the SD feed is pristine (such as HBO, DVD, etc..), the inferiority of signal will be more apparent since any shortcomings that SD contain will be quadruple and more noticable.

At least that is the way I understand it :D

[edtyct]

Smokey's on the button. Analog TV carries comparatively little information, often on the order of 240 vertical lines. Digital HDTVs have 720, 768, and 1080 vertical lines, and a whole bunch of horizontal lines, that have to be activated to fill their screens. Digital HDTVs have to make up the difference between their native resolution and SD resolution by extrapolating--scaling or upconverting--from the meager data at their disposal. But the detail produced by this video processing is completely artificial; it's like trying to satisfy a hungry stomach with pictures of food rather than real food, or to fill a hole in the ground with what's already at the bottom (though high-quality scalers can minimize the damage). The result is a much softer, hazier picture than a true HD or ED source would provide. When you add the problem of deinterlacing this analog material to show on a digital display, the flaws become even more pronounced.

On the whole, analog CRTs have an easier time with analog SD than fixed-pixel displays, since they can scan it natively--that is, they don't have a predetermined pixel count to activate all at once for the screen to fill. But SD won't look too good on a large CRT either; they also scale and deinterlace. All HDTVs are made to put their best feet forward with higher resolution material.

Size of the display, whether CRT or fixed-pixel, matters when it comes to how SD looks on screen. In this case, the smaller the screen, the tighter will the images appear, since the information gaps aren't so easy to see. What we watched as kids on small NTSC sets was no less flawed than its equivalent today. The sets were just too small for us to notice, and we didn't have the benefit of the consciousness raising that larger, HD sets have provided.

SD content from stations like HBO might look more refined because they originated from a more resolved source. The non-HD digital broadcast stations can look as good as the DVDs with which they share resolution. But most people at proper seating distances can tell the difference between DVD (ED) resolution and HD resolution. It's all about the pixels (or scan lines). On an ED (480x720) 42" plasma, however, a DVD might look better than on certain HD panels, since the pixel counts of the display and souce material match exactly; no data had to be created wholecloth to fill the screen.

[cam]

Woodman who? Who needs Woodman when we got edtyct. Just wanted to pass a thank-you for always taking the time to knowledge us less fortunate when it comes to displays. Grumpy old Woodman (AR's last display guru) never came across as wanting to take the time you do. AR sure has an asset with you. Hopefuly eric never chases you away.

[TheHills44060]

Woodman has helped me out quite a few times over the years so i have to stick up for the guy but yeah, great info edtcyt...thanks