The chart you linked to and the article is incorrect. .....
Here is possibly a better chart:
http://cdn.avsforum.com/4/4c/900x900px-LL-4cd4431b_200ppdengleski.png
Yes it is off as get down to normal range of computer monitor screen sizes. The other one isn't to much better as shrink down to smaller portable sizes. It reads about 2 ft for a 9-10" screen... which toasts the iPad.
Sigh. Ran some numbers through a online calculator that seems to check out ( it uses 3438 pixels per inch which is close to the "1 foot corresponds to a dot size of about 89 micrometers or a pixel density of 286.5 dpi. " mentioned here.
http://www.edibleapple.com/2010/06/...display-claims-but-who-the-hell-really-cares/ )
Pretty calculator:
http://isthisretina.com/
bare bones :
http://bhtooefr.org/displaycalc.htm
Anyway some computer monitor sizes mixed in with some real products:
dimensions ___ screen size ---> needed PPI for Retina and viewing distance.
3840x2160 __ 32" ------> 138 PPI 24 inches (64cm ) <== Sharp 32" IGZO 4K monitors $4K.
3840x2160 __ 31" -----> 142 PPI 24 inches (61cm)
3840x2160 __ 30" ----> 146 PPI 23 inches ( 58cm)
1920x1080 __ 30" ----> 73 PPI 47 inches ( 119 cm)
3840x2160 __ 27" ----> 163 PPI 21 inches (53cm)
2560x1440 __ 27" ----> 108 PPI 32 inches (81cm ) <== Apple 27" $999
3840x2160 __ 21.5" ---> 204 PPI 17 inches ( 43 cm )
1920x1080 __ 21.5 ---> 102 PPI 34 inches ( 86cm ) <=== current 21.5 iMac
Most folks don't put the computer's monitor 4 feet away. (48"). So if can see difference at 30" has something to do other than Retina. Deeper and/or more accurate color reproduction perhaps. ( areas where Apple has been ignoring issues in their persuit of the "pixel count increase war" ). Or a bit of "pixel doubling" ( amounts to better dithering. )
There is what might be a dated ergonomics page on Apples site. Apple's ergonomics page has typical monitors placed 18-24" away
(
http://www.apple.com/about/ergonomics/vision.html ). That doesn't look like a heft 27" screen (or iMac though).
I think this page might be a little more current (given the growth in deployed median screen sizes):
"...The screen should be at least 20 to 26 inches distance. Adjust this distance for your visual acuity needs and comfort. The farther away the better in most cases. Distances of 30-40 inches are frequently preferred. "
http://ergonomics.ucla.edu/component/content/article/83-injuries-and-prevention/106-eye-strain
Hmmm, 30-34 inches ... right where that slides the iMacs into Retina zone. Coincidence???
Also Apple will MOST CERTAINLY release a 4k display. It will probably be called Retina Display, but it will support at least 4k. Maybe next year? It's not going to be cheap.
So they could solve a problem that is already done and make a big deal out of it. The real intent is to move from 'current' TV screen requirements to possible next generation TV screen requirements. That keeps panel production numbers high and Apple's costs down.
Also, 4k is not hype, it is real, and it is amazing.
Hype has nothing to do with being real or not. It has to do with being over promoted and becoming more of a buzz word. At this point marketing folks are pitching 4K because every one else is pitching 4K. A year or to ago in TVs it was 3D. that didn't really fly so now it is 4K. NHK is doing 8K demos.
Can 4K be distributed well? Nope. 4K movies into theaters... sure there are solutions. Mass distribution.... no. ( H265 makes HD cheaper and more effective as much as it brings 4k into the perhaps tractable range).
HD didn't really take off until broadcast bandwidth was redistributed. 4K isn't going to get another redistribution.
So it is alot like "the bridge to no where". That existed, but who was actually using it?