3 ms·

I totally don’t understand what this chart is trying to expose. What is meant by the distance here?

by jb1991 6y ago

iso1631 6y ago
Distance from eyeball to screen. There are 2 things this page shows, one is the size of screen you need relative on the distance you sit from it based on how much of your view you want it to fill, the other is what resolution the screen needs to be before you have no improvement. First decide what you want 30 degrees means you'll be able to focus on the picture, but it will fill your focus area, that's recomended by SMTPE 40 degrees is the "immersive" portfolio recommended by THX, you may lose some detail at the edge of the screen depending where you're looking. Then it's just a bit of trig to work out the size you need for the distance you are sitting (or vice versa), to match your preferred "fullness" Second is whether you'll benefit from more pixels. They base this on having 20/20 vision and your optical resolution being 1 arc-minute (1/60th of a degree). For comparison the moon is about 30 arc minutues wide. Seems reasonable to me, if I take a picture of the moon and shrink it to 30px by 30px, I feel it's on par with what I can see in real life. Then it's just more trig to work out how many pixels you need for a given size/distance combination. A 20" screen that's 10 feet away, you won't be able to tell the difference between SD and HD. A 40 inch monitor 2 feet away and you'll benefit from going higher than 4k. (This assumes a 16:9 aspect ratio).
- BlueTemplar 6y ago
  Except they are probably wrong... https://news.ycombinator.com/item?id=26088890 https://news.ycombinator.com/item?id=26088890
  - iso1631 6y ago
    Well they're quoting a definition of "20/20" vision from a researched article on wikipedia https://en.wikipedia.org/wiki/Visual_acuity https://en.wikipedia.org/wiki/Visual_acuity Which states "At 6 metres or 20 feet, a human eye with that performance is able to separate contours that are approximately 1.75 mm apart" Which I assume comes out at 1/60th of a degree. You could argue that measurement is in fact wrong, or that there's something happening subconciously, but their point is that based on accepted viewpoints that someone with 20/20 can't determine the difference between two contours 1mm apart from 6 metres, you don't need to display them. NHK by the way put a lot of money into developing 8k technologies, I saw it about 10 years ago. I was more impressed with the 120fps stuff than the higher resolution. YMMV.
    - BlueTemplar 6y ago
      Why would they use a 20/20 vision as an example, when the average is much better ? Do you think it just a coincidence that the best 35mm film also seems to top out around '12k' ? I'm also much more impressed by HDR than resolutions better than FullHD, but still...
      - leoc 6y ago
        >Do you think it just a coincidence that the best 35mm film also seems to top out around '12k' ? Part of the reason (AFAIK; not an expert) for the very high quality of 35mm is that it leaves enough headroom to crop the filmed image significantly without a noticeable (or at least an obtrusive) drop in image quality. That provided the very useful ability to apply some "analogue digital zoom" in post-production.
      - iso1631 6y ago
        When retina came out, Jobs said that you needed 300ppi at 12 inches. Soneira said it was 477ppi. 1 inch at 12 inches is 4.76 degrees, so Jobs is 63 pixels per degree. Soneira is 100 pixels per degree. Assuming a 16:9 display: If you are at 1.5m/60 inch from a 50 inch display, to meet Jobs's criteria you need 1455 lines -- so 4k (2160 lines). You need 2309 lines for Soneira's criteria. You get 40 degree coverage which is the upper bounds of THX. If you are at 1.7m/66" from a 50" display, to meet Jobs's criteria you need 1326 lines -- so 4k (2160 lines). You need 2104 lines for Soneira's criteria. You get 36 degree coverage width wise which is the "perfect" bounds of THX. If you are at 2m/80" from a 50" display, to meet Jobs's criteria you need 1098 lines -- so 1080p is fine. You need 1742 lines for Soneira. You get 30 degree coverage. If you are at 3m/120" from a 50" display, to meet Jobs's criteria you need 735 lines -- so 1080p is fine. You need 1166 lines for Soneira, so you're only just out of that criteria. You get 20 degree coverage. If you are 30cm/12" from a 7.4" display, you need 1083 lines (Jobs) and 1719 (Soneira), and get 30 degree coverage. My own TV is c. 3m and 42", which I don't think is abnormally small from what people really have for living room TVs. That's 17 degrees, and needs 981 lines for Soneira's requirement, which 1080p does just fine. If you have a large screen or sit very close to it (so 30 degrees), and are looking for a better-than-retina display, then sure, 4k is for you. For a home theatre where you're aiming for 36 degrees then certainly you'll want 4k For the average person with an average tv though, I don't see the extra pixels of 4k being that important compared with a good viewing position, good lighting, good setup of the screen Like the megapixel wars in cameras a decade ago, we're at the point where more pixels doesn't necessarily mean better. 4k, sure, it wouldn't be my prime consideration, but as almost all new TVs of living room size are 4k it's a given. I'd rather a 1080 TV with 6 HDMI inputs than a 4k TV with two inputs though. I had the misfortune of watching the final season of game of thrones on some streaming platform from Sky (UK), at about 4 or 5mbit. It was awful, and that was nothing to do with the resolution.

I totally don’t understand what this chart is trying to expose. What is meant by the distance here?

by jb1991 6y ago

I totally don’t understand what this chart is trying to expose. What is meant by the distance here?

Distance from eyeball to screen. There are 2 things this page shows, one is the size of screen you need relative on the distance you sit from it based on how much of your view you want it to fill, the other is what resolution the screen needs to be before you have no improvement. First decide what you want 30 degrees means you'll be able to focus on the picture, but it will fill your focus area, that's recomended by SMTPE 40 degrees is the "immersive" portfolio recommended by THX, you may lose some detail at the edge of the screen depending where you're looking. Then it's just a bit of trig to work out the size you need for the distance you are sitting (or vice versa), to match your preferred "fullness" Second is whether you'll benefit from more pixels. They base this on having 20/20 vision and your optical resolution being 1 arc-minute (1/60th of a degree). For comparison the moon is about 30 arc minutues wide. Seems reasonable to me, if I take a picture of the moon and shrink it to 30px by 30px, I feel it's on par with what I can see in real life. Then it's just more trig to work out how many pixels you need for a given size/distance combination. A 20" screen that's 10 feet away, you won't be able to tell the difference between SD and HD. A 40 inch monitor 2 feet away and you'll benefit from going higher than 4k. (This assumes a 16:9 aspect ratio).

BlueTemplar 6y ago
Except they are probably wrong... https://news.ycombinator.com/item?id=26088890 https://news.ycombinator.com/item?id=26088890
- iso1631 6y ago
  Well they're quoting a definition of "20/20" vision from a researched article on wikipedia https://en.wikipedia.org/wiki/Visual_acuity https://en.wikipedia.org/wiki/Visual_acuity Which states "At 6 metres or 20 feet, a human eye with that performance is able to separate contours that are approximately 1.75 mm apart" Which I assume comes out at 1/60th of a degree. You could argue that measurement is in fact wrong, or that there's something happening subconciously, but their point is that based on accepted viewpoints that someone with 20/20 can't determine the difference between two contours 1mm apart from 6 metres, you don't need to display them. NHK by the way put a lot of money into developing 8k technologies, I saw it about 10 years ago. I was more impressed with the 120fps stuff than the higher resolution. YMMV.
  - BlueTemplar 6y ago
    Why would they use a 20/20 vision as an example, when the average is much better ? Do you think it just a coincidence that the best 35mm film also seems to top out around '12k' ? I'm also much more impressed by HDR than resolutions better than FullHD, but still...
    - leoc 6y ago
      >Do you think it just a coincidence that the best 35mm film also seems to top out around '12k' ? Part of the reason (AFAIK; not an expert) for the very high quality of 35mm is that it leaves enough headroom to crop the filmed image significantly without a noticeable (or at least an obtrusive) drop in image quality. That provided the very useful ability to apply some "analogue digital zoom" in post-production.
    - iso1631 6y ago
      When retina came out, Jobs said that you needed 300ppi at 12 inches. Soneira said it was 477ppi. 1 inch at 12 inches is 4.76 degrees, so Jobs is 63 pixels per degree. Soneira is 100 pixels per degree. Assuming a 16:9 display: If you are at 1.5m/60 inch from a 50 inch display, to meet Jobs's criteria you need 1455 lines -- so 4k (2160 lines). You need 2309 lines for Soneira's criteria. You get 40 degree coverage which is the upper bounds of THX. If you are at 1.7m/66" from a 50" display, to meet Jobs's criteria you need 1326 lines -- so 4k (2160 lines). You need 2104 lines for Soneira's criteria. You get 36 degree coverage width wise which is the "perfect" bounds of THX. If you are at 2m/80" from a 50" display, to meet Jobs's criteria you need 1098 lines -- so 1080p is fine. You need 1742 lines for Soneira. You get 30 degree coverage. If you are at 3m/120" from a 50" display, to meet Jobs's criteria you need 735 lines -- so 1080p is fine. You need 1166 lines for Soneira, so you're only just out of that criteria. You get 20 degree coverage. If you are 30cm/12" from a 7.4" display, you need 1083 lines (Jobs) and 1719 (Soneira), and get 30 degree coverage. My own TV is c. 3m and 42", which I don't think is abnormally small from what people really have for living room TVs. That's 17 degrees, and needs 981 lines for Soneira's requirement, which 1080p does just fine. If you have a large screen or sit very close to it (so 30 degrees), and are looking for a better-than-retina display, then sure, 4k is for you. For a home theatre where you're aiming for 36 degrees then certainly you'll want 4k For the average person with an average tv though, I don't see the extra pixels of 4k being that important compared with a good viewing position, good lighting, good setup of the screen Like the megapixel wars in cameras a decade ago, we're at the point where more pixels doesn't necessarily mean better. 4k, sure, it wouldn't be my prime consideration, but as almost all new TVs of living room size are 4k it's a given. I'd rather a 1080 TV with 6 HDMI inputs than a 4k TV with two inputs though. I had the misfortune of watching the final season of game of thrones on some streaming platform from Sky (UK), at about 4 or 5mbit. It was awful, and that was nothing to do with the resolution.