billsharpe said:
Sitting about ten feet away from my 40-inch Sony I can't really notice any difference between a 720p and a 1080i picture...
You must be seated within 5.2 feet to fully resolve 1080i on a 40" TV.
You must be seated within 7.8 feet to fully resolve 720p on a 40" TV.
You must be seated within 13.9 feet to fully resolve 480i on a 40" TV.
At 10 feet, you are getting some benefit of HD resolution, but not very much, and as you say, certainly not enough to be able to visually detect the difference between HD resolutions. IOW, our eyes are unable to distinguish resolutions that high at that distance from a screen that size.
This links directly to a handy little Java calculator to render proper seating distances or screen size choices for particular situations:
http://myhometheater.homestead.com/viewingdistancecalculator.html
For the OP, there is one caveat to look out for when looking at the resolution that your TV is reporting to you, and that is that the DVR commonly rescales the resolution of anything not already at the resolution it outputs (you can bypass this and see exactly what the incoming resolution is if you place the DVR in "Native On" mode). Even if you are watching a 720p program (anything from ABC, FOX, ESPN, or MyTV are those that come to mind) your TV will report 1080i if that is how your DVR is set.
Generally speaking, the best practice is to set your DVR to output only 1080i and 1080p modes, and keep 1080i selected for all broadcasts. "Native On" is an alternate solution, but it can aggravate how long it takes to acquire a channel during channel changes or input changes, and really has no actual benefit unless you use a very expensive outboard scaler unit (the one built into any modern TV should be as good; outboard scalers are all but obsolete since a chip-based scaler in a TV can do about the same job just as transparently).
The thing to avoid is setting the DVR output to 720p (or 480p or 480i). These settings are not recommended for a 1080p TV, and are there for backward compatibility only. If you selected 720p that would lower the perceived resolution of 1080i sources, and you don't want that. 1080i will also rescale 720p sources up to 1080i, but that is normal (the perceived resolution will remain at 720p).
The other thing going on here is deinterlacing, but you don't really need to worry about that. Modern flat-panel TVs are all progressive, and must deinterlace 1080i signals to 1080p for viewing. If you set your DVR to output 1080i, it will also then
interlace 720p signals, which are by their nature progressive and not interlaced. The TV then deinterlaces the upscaled and interlaced (previously 720p) 1080i signal to 1080p. So with the DVR set to 1080i, 720p signals are not only upscaled to 1080, but also sent through an interlace (in the DVR)/deinterlace (in the TV) process, which is otherwise unnecessary. The good news is that it doesn't matter; it is completely transparent and will not degrade the picture.
