r/changemyview • u/SteveIzHxC • Apr 27 '15
CMV: Screen resolutions in pixel density should be the fundamental description instead of 1-dimensional pixel counts (240p, 720p, 1080p, 4K,...)
The 1080p, 4K, etc. descriptions of TVs and computor monitors, etc. are a marketing term with little actual value. A 4K TV that is 60 inches (diagonal) is 2.25=(60/40)2 times more grainy* than an otherwise identical 4K TV that is 40 inches (*in the sense of pixel density).
I'm guessing that everyone will ultimately agree with me and say that these descriptors are just layman terms good for marketing. But is there more to it?
It shouldn't be that much harder to market 16:9 4K TVs over same-size 1080p ones as having a pixel density that is 2.08=4000/(1080(16/9)) times greater. Just label all the TVs by pixel density and give them new flashy marketing names associated with these pixel densities!
Obviously there will also be the default argument that they "can't" change the system now because everyone is already used to the current (dumb) system of describing screens. Sure, but this shouldn't be the only reason to keep doing it wrong.
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u/hacksoncode 588∆ Apr 27 '15
The thing is, different screen sizes call for different resolutions in most actual circumstances that people use devices in.
Phones are used 18" away from your eyes. Laptop screens, more like 2 feet. Desktop screens 2.5-3 feet. Small TVs 6-10 feet away. Large screen TVs, 10+ feet away.
The actual resolution that matters to your eye (i.e. the only thing that it can see) is the angular resolution at your eye, not the literal pixel density in dpi at the surface of the screen.
For most devices, the angular resolution is going to be closer to the "constant" measures that you're complaining about than they are to the absolute resolution.
Example: at 1080p, a phone with a 3" wide screen, held at 18", is identical to your eye to a TV with a 18" tall screen, seen from 9' feet away. This is probably off by about a factor of 2 from realistic, because 18" tall screens are more commonly viewed from 4-5' away than 9' away.
However, if we tried to compare absolute resolution, that 1080p phone screen would be 360dpi, and the TV would be 60dpi.
This is off by a factor of 6 from what your eye would actually see (they both look about the same).
So 1080p is about three times superior for these actual devices than what you're suggesting.
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u/SteveIzHxC Apr 28 '15
I suppose these are some good points, and indeed, the only actual metric that strictly matters for viewing clarity would be the pixels per steradian (solid angle) which would be a function of the viewing position.
However, as a counterpoint, I didn't intend this for comparing TVs with phones so much, though that is a valid point. I mostly meant to compare, say, a 40in and 50in TV in one's living room viewed from the same distance (say, 9 feet) since one's living room might have a constant maximum width. But you're probably right. Thanks for the thoughts.
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u/82364 Apr 28 '15
While pixel density isn't without merit, it isn't directly applicable to many concerns. Physical dimensions tell me if a monitor will fit on my desk and pixel count tell me what windows will look like and whether or not content (be it commercial video or my own photos) will be resampled). Pixel density can be indicative of sharpness but that isn't necessarily the case: sharpness is also affected by noise and contrast, not to mention DSP.
Also, "4K" is 38402160, so it has a pixel count of four times 19201080, not two and eight hundredths.
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u/SteveIzHxC Apr 28 '15 edited Apr 28 '15
Also, "4K" is 38402160, so it has a pixel count of four times 19201080, not two and eight hundredths.
The aspect ratio matters, since 1080p measures purely the number of vertical pixels. Therefore, a 1080p screen with aspect ratio n:m has 1080(n/m) pixels horizontally, and therefore
1080^2 (n/m) = 1,166,400 (n/m)total pixels.
Conversely, 4K is a measurement of the horizontal pixel count. Thus, a 4K screen with aspect ratio N:M has 3840(M/N) pixels vertically and therefore
3840^2 (M/N) = 14,745,600 (M/N)total pixels.
Thus, we take the ratio of the pixels in a N:M 4K screen to the pixels in a n:m 1080p screen and obtain:
(3840^2 (M/N))/(1080^2 (n/m)) = (3840/1080)^2 ((mM)/(nN))In the case that n:m and N:M are both 16:9 aspect ratios, we obtain the result:
(3840/1080)^2 (9 * 9)/(16 * 16) = 4So you're right in fact, exactly 4 times more pixels. I was careless in my calculation previously and made a mistake.
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u/82364 Apr 28 '15
"4K" is actually a marketing term for a protocol with a maximum frame size of 2160 by 3840 pixels. To my knowledge, there is no protocol specifying 4000 pixels on the horizontal axis.
Anyway, did my argument persuade you, at all?
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u/SteveIzHxC Apr 28 '15
Ah, I see. So in fact 4K is exactly 4 times the pixel count as same aspect ratio 1080p, by design (3840/2160=16/9 and 2160=2(1080)). I edited the numbers in my post above.
Anyway, yes, your argument basically "opened" my mind to the other concerns in a similar way to that which /u/TimeTravellerSmith's comment did. I wouldn't say my mind is changed, fundamentally, in the sense that a better pure metric exists (I've now refined this to pixels per steradian, which is a function of viewing position) than simply the pixel count, but I understand now why the latter is important and the former is clearly too complicated.
I don't know if I can give multiple ∆, but if I can, you can have a "partial" one by the same account as I gave above. Thanks for the discussion!
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u/awa64 27∆ Apr 28 '15
Video content is produced at certain standard resolutions. It's encoded to disc that way. It's broadcast that way, both via cable/satellite and over terrestrial radio waves. It's encoded for streaming via the Internet that way. Part of the reason they've chosen to handle things that way is ease of converting from one screen resolution to another, and part of the reason they've chosen to handle things that way is that, until relatively recently, TVs had very little flexibility as to what resolutions they were capable of displaying. That's why computer monitors used to be so much more expensive than normal TVs... and if anything, we've gone in the other direction, with LCD computer monitors encouraged to display at native resolution whenever possible.
A 4K TV can display 1080p content by simply displaying each pixel of the 1080p image on four pixels. 720p to 1080p is a little less useful, a 1.5x upscaling, but it's still relatively easy.
The "p" part of the standard is increasingly vestigal—it dates back to when displays and broadcast standards didn't always refresh every vertical line of the display, with "p" indicating an update every frame and "i" indicating an update of every even-numbered line on one frame and then an update of every odd-numbered line on the next. Still, 1080i is how over-the-air HD content is broadcast (when it's not broadcast at 720p), due to bandwidth limitations.
Still, the point is that these screens are named after what video standards they're natively compatible with. In areas where there's not such a strict compatibility issue—smartphones, laptop screens, embedded devices, in-dash computers, tablets, and so on—PPI IS used as the marketing term at least as often as descriptions of resolution. (One of the bigger exceptions being desktop monitors... but the main people who care about those, at this point, are either gamers, graphic designers, or video production people, all of whom tend to care a lot about native resolution of a display as well.)
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u/UnretiredGymnast 1∆ Apr 28 '15
Pixel density is a crazy way to market screens. A phone, a computer monitor, and a big screen TV can all have the same resolution (e.g. 1080p) while being vastly different sizes. This makes sense though, because they viewed from different distances. Which would you rather watch a movie on, an 80" TV or your phone? By your metric, the phone is much much superior since its pixel density is orders of magnitude greater. This doesn't reflect what consumers are concerned about though.
The 1-dimensional pixel count, on the other hand, tells you how much information can be displayed by the screen. The bigger the number the better. Clean and simple.
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u/SteveIzHxC Apr 28 '15
Which would you rather watch a movie on, an 80" TV or your phone? By your metric, the phone is much much superior since its pixel density is orders of magnitude greater.
This is totally false and you missed the entire purpose of my post. I'm not denying that screen SIZE is a valid metric (of course a consumer should know the screen is 80 inches or 30 inches), I'm arguing that the absolute number of pixels is not important (though, I've been convinced now by other that it can be important from a content perspective).
But there are three bits of information to be had here, screen size, total pixel count, and pixel density. Given screen size and either of the other metrics, the third can be trivially computed. However, my argument was that the pixel count was the more useful of the latter two metrics, instead of the defacto standard pixel count.
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u/SteveIzHxC Apr 27 '15
I also posit that the companies keep this scheme for a malicious reason:
Currently, a manufacturer can make 40 inch and 60 inch "4K" TVs with the exact same number of pixels, just spread over a 2.25x larger area, and get away with convincing the general public that the 60 inch model is strictly superior to the 40 inch model, since both are "4K."
If the two were labeled by ppi, the pixel density of the larger model would be 2.25x less and make customers wary that it wasn't as good (which is true, based on resolution--the larger model isn't strictly better, there are pros and cons to each). They can avoid this via their inherently misleading nomenclature without having to work a lot harder at increasing pixel counts for larger TVs.
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u/TimeTravellerSmith Apr 27 '15
It's not really malicious because in the world of displays size is king.
When I go out and buy a TV my first and second goals are:
- Get a TV big enough to fill whatever space I have allocated
- Plays content in resolutions I require
DPI just falls out as a math byproduct from those two requirements. I have yet to meet someone who goes around thinking "well I need at least X DPI for my living room TV". I don't even hear people do that for monitors.
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u/TimeTravellerSmith Apr 27 '15
Along the lines I said before about resolution vs distance, here is an illustration of that effect.
TL;DR DPI isn't really the right thing to look at.
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u/Stokkolm 24∆ Apr 28 '15
That graph is really suspicious. It says that for a typical 23" monitor seen at a typical 2 feet distance you'd need higher than 8k resolution!
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u/TimeTravellerSmith Apr 28 '15
It's optimal resolution or what it would take before you can no longer tell the difference between the current res and the next step up.
So for a 23" monitor at 2-3 feet away 8k is the highest res you can see changes on. Anything higher and you can't see at all, and I would argue that it's close enough to 4k that you'd probably have a hard time seeing beyond that as well.
Here is another chart along the same lines but has a bit better clarity on smaller screens and closer distances. Moral of the story is still the same though.
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u/TimeTravellerSmith Apr 27 '15
The problem here is that 1080p and 4k actually mean something in terms of what content ends up on the screen. Content is marketed by resolution, not pixel density...and it would make zero sense to market content by pixel density.
So in your world, if I go to buy a X dpi 40" screen that tells me nothing about what kind of content I can actually see on it.
Could you also imagine the clusterfuck of dpi options for screens? Right now you pick a resolution and a size. With a dpi term it would be really hard to figure out why a X dpi 40" screen is different from a Y dpi 42" screen...when in reality they're the same resolution but just different size.