Originally Posted by matteos
Agree, I just got updated with a 2560x1440 screen at work, the size is nice but I have it next to my old monitor which is 1680x1050, the only discernable difference even up close is that text and icons are smaller because apple won't let you adjust the size of them... Image quality? video quality? no difference. For a TV where you are sitting at least 6 feet back I think 4k is likely a waste of time, still it will drive down the price of existing sets
The reason you are not seeing a difference, is because most monitors are roughly the same pixel density, with 27" 2560x1440 displays being around 110 PPI. Your 1680x1050 display may be an exception though, if things now appear smaller. I'm guessing it was a 20" (100 PPI) or 22" (90 PPI) screen rather than an 18" one. (110 PPI)
Because computer monitors have traditionally increased resolution more-or-less linearly with screen size, this roughly 100 PPI density has remained relatively constant over the years, and so all that happens when you get a new "high resolution" display is that it's bigger and you have more workspace, or things get smaller on-screen if it's higher density, as you have seen.
When you quadruple the screen resolution (double the pixel density) however, you are then able to take advantage of Apple's "HiDPI" mode, which keeps all UI elements and text the same size, but renders objects with 4x the detail.
Rather than everything getting tiny
when going from 1920x1080 on a 22" display (100 PPI) to 4K on a 22" display (3840x2160, 200 PPI) your workspace will remain the same, but text and images will be significantly clearer/sharper and more detailed, similar to what Apple has just done with the new iPad
You can see this for yourself if you have an iPad 3 and AirDisplay, as they have added support for Apple's HiDPI mode, so you can have a 1024x768 sized workspace to keep text and icons at a good size (though actually the screen is so sharp, I find 2048x1536 perfectly usable) but with a considerably sharper and more detailed image than natively running at 1024x768. (which looks terrible in comparison)
For example, here is a side-by-side comparison between Safari and Google Chrome on the iPad via AirDisplay. You have the equivalent workspace of a 1024x768 screen, but Safari supports HiDPI mode, rendering the page at 2048x1536, whereas Chrome does not, and renders the page at 1024x768.
Pixel density has far more of an impact on things than resolution
does. I am now mainly using a 46" display, which only has a density of 48 PPI, and looks quite bad when you use it as a monitor. Going to 4K would only bump this up to 96 PPI—still lower density than current
computer displays, and this year we are likely to finally start seeing computer displays move towards 200 PPI.