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It's the difference between the movie industry and TV industry. TV has always described resolution in "lines", because only the vertical direction had a fixed

by lambda 13y ago

It's the difference between the movie industry and TV industry. TV has always described resolution in "lines", because only the vertical direction had a fixed number of lines, the horizontal was analog and thus there wasn't a specific number of lines (there was a maximum frequency it could display accurately, and thus a minimum feature size, but no discrete "lines"). So, SD NTSC is 480i (i for interlaced), PAL is 576i. Actually, NTSC was really 525 lines, but some of them were not visible and part of the blanking interval. When you started moving into HD, they kept this convention, referring to 720p, 1080i, 1080p, etc. When movies started being distributed in digital formats, the movie industry chose a different standard of naming the resolutions, calling it 2K for 2048x1080. I'm not sure why they chose to focus on the horizontal rather than vertical resolution like the TV industry, but there you go. So the 2K/4K terminology comes from the movie industry, 720/1080 from TV. Just be glad that we're using this term and not the computer industry term for it, which is WQUXGA (edit: sorry, QFHD, WQUXGA has 2400 vertical pixels, not 2160, see how memorable these names are?), though it is frustrating that "4K" is used for something that doesn't actually have over 4000 pixels in either dimension. In fact, this doesn't meet the official definition of 4K, it's actually just 4 times the size of 1080p, so it would be more appropriate to name it 2160p or QFHD instead of 4K. But for some reason, 4K has become the de-facto buzzword for this generation of resolutions, so it's what we're stuck with.

twic 13y ago
I wonder if the film industry refers to horizontal resolution because they've historically referred to film by the horizontal dimension of the film: a 35 mm film strip is 35 mm wide, 8 mm is 8 mm wide, etc. Admittedly, those are the widths of the film strips rather than the frames, so there is no direct correspondence here, and there are formats (such as IMAX) which run the strips horizontally, so the width of the strip constrains the height of the frame, rather than its width. But this is my story and i am sticking to it.
- lambda 13y ago
  Ah, that's a good point. On film, the horizontal size is the constraining factor, and they can choose how much vertical real estate to use per frame to give the aspect ratio they would prefer.

by lambda 13y ago

twic 13y ago

I wonder if the film industry refers to horizontal resolution because they've historically referred to film by the horizontal dimension of the film: a 35 mm film strip is 35 mm wide, 8 mm is 8 mm wide, etc. Admittedly, those are the widths of the film strips rather than the frames, so there is no direct correspondence here, and there are formats (such as IMAX) which run the strips horizontally, so the width of the strip constrains the height of the frame, rather than its width. But this is my story and i am sticking to it.

lambda 13y ago
Ah, that's a good point. On film, the horizontal size is the constraining factor, and they can choose how much vertical real estate to use per frame to give the aspect ratio they would prefer.