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Trying to imagine how close you would have to be to the screen to tell the difference between 1080 and 4k...

by iso1631 5y ago

true_religion 5y ago
Surely, sitting in front of a laptop or iMac would make it easy to tell.
- iso1631 5y ago
  "on a phone" SMPTE suggest that 4k for viewing is only worthwhile for people with 20/20 vision once the viewing angle increases beyond 30 degrees. I'm currently looking at a 40cm wide screen, I'm 80cm away from it, which is about 30 degrees. For my phone to fill that amount of space it would have to be about 10cm in front of my eyes due to binocular vision (if I just use one eye it's a bit further When I watch something on my phone it's typically 50cm away, about 15-20 degrees viewing. 720p is more than enough at that size, 1080p if you have particularly good eyesight.
WithinReason 5y ago
It's hard to tell for uncompressed, but easy for compressed YouTube videos
- LeFantome 5y ago
  Compressed by what? Are you just talking about videos you record on your phone? I do not know what phone you have but an iPhone 12 ( as an example ) is under 1300 pixels on the short dimension. So you are not getting much more than 1080 pixels no matter what. It seems any experiential difference would have more to do with compression quality than with resolution. Speaking for myself, I do not think I could tell the difference between 4K and 1080p on a phone ( on a decent AV1 clip ).
- wyldfire 5y ago
  But doesn't YouTube negotiate a "channel sized" rate? It seems like it switches between bitrates based on what you can tolerate. All of this is to say that it seems like a tough-to-nail-down metric to evaluate.
- iso1631 5y ago
  So you're saying that a given 4k source compressed to Xmbit will look better if it's not downscaled to 1080p before compression, but instead downscaled by the display (I don't believe there are any phones with a 2160 line display)?
  - WithinReason 5y ago
    4K YouTube videos have a higher bitrate than 1080p videos
  - tedunangst 5y ago
    What they're saying is that a 1080p source upscaled to 4K and then uploaded to youtube and then downscaled by the client to a 1080p screen will look better than a 1080p upload because it has more bits.
    - iso1631 5y ago
      That's nothing to do with the codec or the resolution
      - Dylan16807 5y ago
        The reason it looks better isn't directly codec or resolution. But it does mean that there are reasons to want 4K playback on a phone.
- Rebelgecko 5y ago
  I always assumed that for streaming sites bitrate was a bigger factor
  - iso1631 5y ago
    Of course it is, a 1080p video at 10mbit will almost always look better than a 4k video at 1mbit, and a 4k video at 10mbit will almost always look better than a 1080p video at 1mbit. The far more interesting question is if you accept you have Xmbit to play with, what is better on a given platform (screen size, resolution, viewing situation, how well compression works, how much battery is used in decoding, etc)
  - brigade 5y ago
    And bitrate goes up for 4k tiers. Even if bitrate only doubles for 4x the amount of pixels, that'll probably look better with modern codecs (depending on where in the quantization curve you are), and most services use at least 3x the bitrate for 4k over 2k, across the same codec.

Trying to imagine how close you would have to be to the screen to tell the difference between 1080 and 4k...

true_religion 5y ago

Surely, sitting in front of a laptop or iMac would make it easy to tell.

iso1631 5y ago
"on a phone" SMPTE suggest that 4k for viewing is only worthwhile for people with 20/20 vision once the viewing angle increases beyond 30 degrees. I'm currently looking at a 40cm wide screen, I'm 80cm away from it, which is about 30 degrees. For my phone to fill that amount of space it would have to be about 10cm in front of my eyes due to binocular vision (if I just use one eye it's a bit further When I watch something on my phone it's typically 50cm away, about 15-20 degrees viewing. 720p is more than enough at that size, 1080p if you have particularly good eyesight.

WithinReason 5y ago

It's hard to tell for uncompressed, but easy for compressed YouTube videos

LeFantome 5y ago
Compressed by what? Are you just talking about videos you record on your phone? I do not know what phone you have but an iPhone 12 ( as an example ) is under 1300 pixels on the short dimension. So you are not getting much more than 1080 pixels no matter what. It seems any experiential difference would have more to do with compression quality than with resolution. Speaking for myself, I do not think I could tell the difference between 4K and 1080p on a phone ( on a decent AV1 clip ).
wyldfire 5y ago
But doesn't YouTube negotiate a "channel sized" rate? It seems like it switches between bitrates based on what you can tolerate. All of this is to say that it seems like a tough-to-nail-down metric to evaluate.
iso1631 5y ago
So you're saying that a given 4k source compressed to Xmbit will look better if it's not downscaled to 1080p before compression, but instead downscaled by the display (I don't believe there are any phones with a 2160 line display)?
- WithinReason 5y ago
  4K YouTube videos have a higher bitrate than 1080p videos
- tedunangst 5y ago
  What they're saying is that a 1080p source upscaled to 4K and then uploaded to youtube and then downscaled by the client to a 1080p screen will look better than a 1080p upload because it has more bits.
  - iso1631 5y ago
    That's nothing to do with the codec or the resolution
    - Dylan16807 5y ago
      The reason it looks better isn't directly codec or resolution. But it does mean that there are reasons to want 4K playback on a phone.
Rebelgecko 5y ago
I always assumed that for streaming sites bitrate was a bigger factor
- iso1631 5y ago
  Of course it is, a 1080p video at 10mbit will almost always look better than a 4k video at 1mbit, and a 4k video at 10mbit will almost always look better than a 1080p video at 1mbit. The far more interesting question is if you accept you have Xmbit to play with, what is better on a given platform (screen size, resolution, viewing situation, how well compression works, how much battery is used in decoding, etc)
- brigade 5y ago
  And bitrate goes up for 4k tiers. Even if bitrate only doubles for 4x the amount of pixels, that'll probably look better with modern codecs (depending on where in the quantization curve you are), and most services use at least 3x the bitrate for 4k over 2k, across the same codec.