Can you use 2160p?
How to calculate your pixels per degree:
dist = your sitting distance from the screen
diag = your diagonal screen size
for 16:9 screens: Horizontal resolution x 0.02 x dist / diag
Or for some popular resolutions:
1280x720 = dist x 25.62 / diag
1366x768 = dist x 27.36 / diag
1920x1080 = dist x 38.45 / diag
for 5:4 screens: Horizontal resolution x 0.0224 x dist / diag
1280x1024 = dist x 28.61 / diag
For 4:3 screens: Horizontal resolution x 0.0218 x dist / diag
1600x1200 = dist x 34.91 / diag
2048x1536 = dist x 44.68 / diag
For 16:10 screens: Horizontal resolution x 0.0206 x dist / diag
1920x1200 = dist x 39.52 / diag
Example if you sit 8 ft away from a 40" 720p screen you see
96 x 25.62 / 40 = 61 pixels per degree in the center of the screen
What does this matter. The higher the pixels per degree you see the more real the picture gets. The current standard for HDTV is set at 60 ppd. That is what the well known chart for screen size and seating distance is based on.
http://www.blogcdn.com/www.engadget.com/media/2006/12/resolution_chart.jpg
The SMPTE HDTV standard further agrees with this number, advising an optimal field of view of 30 degrees. That corresponds to a seating distance of 1.63 x diagonal screen size, which equals 62.5 ppd in the center of the screen.
At 60 ppd you won't be able to see the individual pixel elements anymore. However studies done by NHK show that people perceive a big benefit going to 100 ppd, and can even perceive differences between picures upto 200 ppd. 200 ppd is considered to be the edge of human visual acuity. Beyond that you won't be able to tell if you're looking through a window or at a display screen.
Super Hi-vision or 8K video (8192x4320) is based on this research. Also known as UHDTV (7680x4320)
http://www.engadget.com/2012/07/31/super-hi-vision-eyes-on
http://www.dpreview.com/news/2012/08/01/8K-video-and-gigapan-images-bring-olympics-in-high-resolution
At 200 ppd UHDTV screen sizes aren't unreasonably big to fit in your home.
http://www.avsforum.com/t/1416475/viewing-distance-chart-720p-vs-1080p-vs-4k-vs-8k-and-beyond
At 8ft an UHDTV screen would be 73" diagonal. (dist x 0.769) By the time 8K arrives those screen sizes will be common. At that distance you will have a field of view of 37 degrees, still a little under the optimal field of view specified by THX requirements which is 40.04 degrees. (sitting at 1.2 * diagonal screen size)
You can see right now what super hi-vision or a reality display looks like. Simply walk away from your screen. You will see 200 ppd at (diag x 5.2) for 1080p sets, or (diag x 7.8) for 720p sets. For example a 40" 1080p set will give you 200 ppd at 17ft4" The iPad 4 retina display needs to be viewed at a distance of 43.4" to make it a true retina display.
Seems a bit far right? Maybe a bit overkill, but looking at test patterns from that distance shows 1 big advantage, no more aliasing problems, no more jaggies.
8k tests are being done now but it will be a long time before consumers see any of it. However 4K (4096x2160) and QFHD 2160p (3840x2160) are on the way. Actually they can't come soon enough. 1080p is a pretty low res for pc monitors considering how close you sit. No wonder 8xMSAA etc are considered a must in pc games.
Going upto 100 ppd makes a big difference. I see it daily going from the wide field of view of a 1080p projector to the much smaller field of view of a 1080p tv. Love the sharpness of the tv, love the wide field of view of the projector.
4K is also what is used in cinema, and what 35mm film can provide. Unfortunately that also means 1 more round of upgrading your movie library.
The first 2160p displays are for sale now (ie if you happen to win the lottery)
http://www.trustedreviews.com/sony-vpl-vw1000es_Projector_review
At about $25,000
http://www.engadget.com/2012/07/19/lg-84-inch-ultra-definition-4k-hdtv/
At about $22,000
The first 4K movie is out too, for $299 shipped on a HDD.
http://reviews.cnet.com/8301-33199_7-57467138-221/first-4k-movie-available-for-sale/
It will probably be another 5 years before 2160p sets become affordable. The first plasma tvs also started at 15k or more back in 1997. Apart from the price there is also little content yet. (Except digital camera pictures. 2160p is 'only' 8.3mp which mobile phones can do already) Ofcourse if you can afford a 2160p set you can also a afford a pc capable of rendering at 3840x2160. Imagine a fully modded version of Skyrim running on that projector.
Anyone else looking forward to 2160p displays?
Some numbers:
1080p = 1920x1080
2160p = 3840x2160 QFHD (quad full high definition) or UHDTV1
4320p = 7680x4320 8K UHDTV or UHDTV2 (ultra high definition TV)
4K = 4096x2160 for consumer electronics
Digital cinema 4K = 4096x1714 (2.39:1) or 3996x2160 (1.85:1)
Academy 4K = 3656x2664 (1.37:1)
Full aperture 4K = 4096x3112 (1.32:1)
8K = 7680x4320 aka super hi-vision
