Originally Posted by Whatever1
So if 60" is the max for 1080 then at 120" would you not see the difference ?
Would a 4K projector upscale 1080 or 720 and would that look better ?
Scaling is always a question mark. Also, the statement that 60" for 1080p means something is not accurate.
Resolution is a matter of viewing distance. Since 'normal' viewing distance is 10' or so, then about 60" (or a bit larger really) with 1080p resolution won't yield any greater performance if you increase the resolution.
Likewise, if you have a 400" screen that you view from 80 feet away, you can stick with 1080p.
It's when you sit closer to larger screens that things really start to make a difference. But, simply increasing resolution on the display, with no concern to the source, won't solve things. You won't notice visible pixel structure if they have minimal inter-pixel gap, but you will notice flaws in the original image. Remember! 1080p streamed is not the same as 1080p from Blu-ray Disc. Likewise, upconverted 1080p, even from a good source, is not the same as quality UHD material. You can't get four times the pixels from thin air. They must be interpolated, and different projectors will handle this conversion differently from each other. You SHOULD expect an improvement since they will use scalers to convert from 1080p to 2160p. But, it will not be the same as quality 2160p native material.
These same discussions, occurred at length when the jump from 720p to 1080p came about. Even more discussion when Blu-ray Disc came along in comparison to DVD.