Why Does My HDTV Have Poor SD Picture Quality?
1. Your HDTV may be a lot larger than your old TV, so it's a bit like putting a magnifying glass to a newspaper. For example, a 50" HDTV is roughly 4 times as large as a 27" TV. Don't sit too close to the TV - recommended minimum viewing distance for SD is roughly 2 times screen size (diagonal measurement).
2. Your HDTV shows a lot more detail than an SDTV and you're seeing all the "poor signal qualities".
3. Your HDTV needs to be set up properly (for each input) - typically lower your sharpness, take the TV off "vivid/dynamic mode" and read the Digital Home FAQ (under help) "What you need to do to your new HDTV".
FAQ - What You Need To Do To Your New HDTV - Canadian TV, Computing and Home Theatre Forums
4. Many times the incoming signal is simply poor. If it's analogue, you may need more signal strength. If it's digital, there may be too much compression and there's not much to be done about the latter. Cable companies are headed towards an all-digital lineup and some already have it.
5. Have a look at the "best looking SD channel." If that one looks "good", then you know it's not the TV, but the reception/signal of the other "poorer" channels. The best SD channel can have roughly the same picture quality as a DVD.
6. If you have just purchased a CRT-based RPTV, they can appear a little "grainy" when new. After about a month, they tend to look smoother.
7. Some cable STBs do not output the best SD (analogue) quality. To test if this is the case, connect the cable directly to your TV's tuner and see whether that makes a difference (especially earlier Motorola STBs). You could then split the cable upstream of the cable STB and view the analogue channels with your TV's tuner (Splitter 1000MHz or 1GHz). You could also consider RF-coax, composite, or S-video connections for the SD channels from the STB to the TV.
8. If you have a STB, make sure you've configured it correctly in the setup menu for 480i signals. Often the "default" settings are not the best and you may be sending the "incorrect/inappropriate" signals to the TV. Many STBs for example come with a "default" setting to convert all incoming signals to 1080i - this may not be the best setup, although with most new STBs, the differences are slight. Many times the best setting is called "passthrough, or something similar", which allows incoming signal to flow unchanged through the STB to the TV - experiment with settings to see what you prefer.
9. If you didn't have digital cable or satellite before you bought the TV, and acquired it at the same time, you may be unfamiliar with digital TV which has certain good qualities but also 'bad qualities' - like compression artifacts...
10. If you have the equivalent HD channel, watch the programme on the HD channel, even if it's upconverted, and not true HD. The upconverters that the affiliates utilize are usually much better than the ones in your TV. Just be careful about burn in if you have a CRT-based TV or a plasma. Remember, SD doesn't HAVE to look bad on an HDTV, and it SHOULDN'T look bad on an HDTV, but there are lots of reasons why it CAN look bad on an HDTV.
11. Analogue channels are subject to interference and degradation with poor signal strength. Digital channels are not subject to the same interference or degradation - they are only subject to the "compression" the service provider does.
12. Although not inexpensive, some people have used scalers (iScan for example) to improve SD PQ. Some people have also had improvements by going "through" a DVD recorder - depends on the STB, Recorder, TV, settings, etc.
13. Not all HDTVs are created equally when it comes to the upconversion of SD signals. Some are better at it than others, although the TV is not what has the largest impact - it's the quality of the signal and the settings on the TV.
14. If you have a TV that's not subject to burn in, then you should not stretch the image. Leave it as 4:3 and you'll have the best PQ and no image distortion. Since most people now watch mostly HD and DVDs, the burn in issue is not as much of an issue as it used to be.
Remember, SD doesn't HAVE to look bad on an HDTV, and it SHOULDN'T look bad on an HDTV, but there are lots of reasons why it CAN look bad on an HDTV.
Please PM me if you do have suggestions for this FAQ and I will consider adding them.