@sixthsense
I was reading patiently all the posts, and I must say nothing comes close when observations are heard from a hands-on situation. Can you please write your research result of "relation between the screen size and viewing (screen to viewer) distance"? I want to hear from you realistically, what size looks how from what distance in full HD
BTW if I ever get to develop 1080p PJ set up, the first two films that I want to see are - LAWRENCE OF ARABIA and DANCES WITH WOLVES
Arnab
This should be more of personal choice and liking. For me I consider the optimum size would fill your view with the image to really get a feel of a movie theatre. Also it takes time to get adjusted to this new size of the screen as you cannot compare it to the TV.
For the TV's ranging from 42 - 55", I think a minimum viewing distance of 8 feet and maximum of 10 feet should be fine. As soon as you go beyond that it just gets worse. I think 3D would not even make an impact at a distance beyond 10 feets. In the showroom that's why you are watching everything at 6-7 feet and you see the hd videos and 3d filling your view and making you go WOW.
Simple calculation for me is too double the size of the screen should be your minimum viewing distance and adding few more should be optimum but not going beyond 2.5 times your screen size. Currently my projector is setup to put a 120" diagonal length image and my seating is around 22-24 feet away from the screen. Anything smaller than that was not suiting me, some friends do say that a bit small would be better but then they are not used to the big screen.
One more thing that can make you decide. When it comes to movies there are two components the visual screen image and the sound. Now with a powerful sound system and all the new formats of DTS HD audio somehow the audio aspect is more over powering in the whole experience when you've a small TV. As you are trying to play the audio to the quality played in theatres but the TV cannot be compared which leaves you with half the experience.
With a big screen, this is balanced and you would be immersed in the movie without the audio overpowering the experience and in fact it will complement your big screen. I would not recommend a Basic HTIB if you are going for a projector.
So last point about the video quality. You can still watch DVD's on the TV upto 55 and they'll still look reasonable to you. But you just cannot play DVD ( maybe HD DVD's are better) on the screen sizes beyond 80", as it looks crap and unwatchable. You minimum need a 720p resolution BR ripped file which is of minimum 4-5 gb size for a 1 hr length video to show up decently on your screen. 1080p or HD would be the way to go and BluRay is the top most quality you can get today. As far as I'm concerned only 1080p rips from BR without any compression looks great and does justice to the equipment.