kurastorm - 2K Resolution rant

TL;DR 1440p is 2.5K not 2K, just call it 1440p

The issue here is sometimes people refer to both 2560x1440 and 1920x1080 as "2K." So how do you know which is correct? arguably both are correct, but personally I think it is wrong to consider 1440p as 2K

3840x2160 aka 4K UHD is called "4K" because the 3840 width is almost 4000 pixels
2560x1440 aka WQHD or just QHD is called "1440p" because the 1440 height
1080p (FHD) and 720p (HD) are also based on height while 8K (8K UHD) aka 7680x4320 is also almost width like 4K

I should mention "4K", "2K", and "1080p" are generic terms not standards. I am operating under the assumption we are talking about 16:9 aspect ratios. 

Resolution standards do exist in the movie industry, DCI (Digital Cinema Initiatives)
DCI 4K is 4096x2160 which is approximately equal to 3840x2160 
DCI 2K is 2048×1080 is ≅ 1920x1080

Finally the math
7680 x 4320 = 33177600 pixels
3840 x 2160 = 8294400 pixels 
1920 x 1080 = 2073600 pixels 

2073600 x 4 = 8294400 pixels
8294400 x 4 = 33177600 pixels

Why 4 and not 2? because the height and width have to be doubled for consistent scaling
(1920 x 2) x (1080 x 2 ) = 2 x 2 x 1920 x 1080 = 4 x 2073600 

When it comes to 5K (5120 x 2880) you see half of its resolution is 1440p, so I call it 2.5K
2560 x 2 = 5120
1440 x 2 = 2880

As far as I can tell the reason people call 1440p "2K" is its width is greater than 2000 pixels, which is true, but also an inconsistent reason when you compare it to the aforementioned resolutions, I don't expect people to call it 2.5K, I would just suggest people don't use the 2K term and continue to use "1440p" and "1080p" to be explicitly clear.