Community Newsletter: Q&A: HDTV buying advice: 720p vs. 1080p

Re: 1080i vs 1080p

In response to remmeler above.

There is actually no "line doubling", the number of lines stay the same. The odd and even frames are simply combined in a method known as de-interlacing. You might be confusing this with the early HD CRT screens that were 960i and used line doubling.

I worked in broadcasting for 3 years and when you have any sports/action/fast motion objects, 60fps is superior to 30fps due to the motion being captured 60 times a second vs 30 times a second. So 720P is a trade-off for smoother motion with lower resolution. With the resolution not becoming a factor on 50" or smaller screens at the optimal viewing distance of 2 x 50" at 8.3' (per the SMPTE (Society of Motion Pictures and Television Engineers) standard, 720P gives you a better experience in many ways with smoother motion.

HD broadcasts are not just 1080i, they are either 720P or 1080i with the SD channels and SD DVD's being 480i.

This means that your 1080P screen is up-converting/scaling all the 720P channels. Native resolutions are always superior to scaled ones since scaling adds noise and artifacts no matter how expensive the scaler is, since your are adding pixels into each frame using interpolation algorithms.

So 720P looks better on a 50" 720P screen vs a 50" 1080P screen everything else being equal. You got to compare apples to apples here. 1080i would tend to look better in most cases on a 1080P screen since the image would only need to be de-interlaced.

My point is that there really isn't a clear cut "better" picture with either format since you are not using native resolutions all the time on either one. There are factors such as screen size, material, native resolution, contrast ratio etc. to consider. But all material looks best when its presented native and without any processing such as de-interlacing or scaling. Altering the original adds noise, artifacts etc no matter how well its done.

So on either screen there will be scaling and de-interlacing used. Down-scaling is always superior to up-scaling due to the fact that discarding material from each frame is a lot easier than adding material to each frame.

This also leads to the fact that down-converted 1080i/P on a 720P screen will in most cases look better than up-converted 720P on a
1080P screen (there is no 720i).

You can easily see this on your LCD computer screen. Adjust the resolution above the native resolution and see how it looks, then adjust your resolution to lower than native. The results will speak for themselves.