How is 4K Ultra HD "Four Times the Resolution" of 1080p? - Page 3 - AVS Forum | Home Theater Discussions And Reviews
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Old 11-08-2014, 02:04 PM
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A couple more tidbits for thought.

What is the difference in scale between 1080 HD and 2160 UHD? If I render an image at 1080, what relative factor of scale would I need to render at 2160? Would that be 400%, or 200%? The 2160 image is only twice as large in any single axis. And it is the single axis alone that defines the relative difference in sharpness, not the 2 dimensional factor of 4 that defines the difference in total image elements.

The only objective way to discern or compare the apparent sharpness of video or film, whether in display or projection, is through the use of linear resolution charts that effectively relate a single axis (dimension) for comparison. Under ideal conditions, with respect to the difference between 2160 UHD and 1080 HD, such charts reveal a difference in sharpness never greater than 2.

Again, as stated upfront in my first post: I agree that 2160 UHD has four times the pixel count of 1080 HD and (as loosely defined by some, but not all) can be referred to as having "four times the resolution." No debate there. What I've tried to illustrate through this and previous posts in this topic (through the use of several different examples and explanations provided with appropriate context) is the argument that it is at best misleading to then suggest, as most manufactures do in their overly-zealous marketing of UHD, that as a result of having "four times the resolution" it is also four times as clear or sharp. That's all.

My posts here have been to provide opinion, and to perhaps reopen a discussion of the topic with others. The purpose of a forum topic such as this is to exchange information: to learn or inform, and sometimes to argue and debate. Whenever I post in any forum setting, I am always mindful that the people I may be communicating with are just that - people. People with experience that is different from mine, and opinions that may not agree with mine. Above all, people that deserve my respect just for the very fact that they are people, not contingent upon what they say.

Have I offended you in some way, tgm1024? Is there really cause provoking your incessant, personally derogatory snarks, such as claiming I resort to " . . . the most childish of arguing techniques . . ." or that my future comments might " . . . pollute this thread any further . . .?"

Or how about other comments you've made that appear to be not-so-veiled attempts to intimidate or bully others into submission, such as "We go through this over and over and over" or "I have no more time for your line of reasoning" or "If you wish to hold your ground on this and fight the uphill battle against the world, be my guest. But you'll lose" or "You need to stop fighting this." And those are just excerpts from this one thread alone . . .

There's a not-so-fine line between commenting and trolling . . .

Last edited by bart.; 11-08-2014 at 06:13 PM.
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Old 11-09-2014, 07:35 AM
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And the troll word surfaces....

Let's take the teeth out of this for a moment.

What I took offense to was this: "From reading your other responses in this thread I get the impression that its doubtful any other facts or evidence presented by myself or others will persuade you, so I'll stop here."

"Facts and evidence" is a conversational attempt to place me in the category of someone refusing to listen to some wave of information. There were no "facts and evidence from others". Evidence? Those were opinions. I've been in the business of image processing and computer graphics for a long time. What I'm talking about comes from that experience, and from how the industry uses the term with regard to displays. And those would be my opinions.

But for a wave of such information, have you done the google search I suggested?

For perceivable clarity it's not about a mere pixel count, because as Joe Bloggs and I pointed out, the pixels have to mean something. But it is about how much information (non muddied, clear information) is present to allow you to discern what's being drawn, or to present it with clarity, or or or or or (choose your own wording, perhaps sidestepping "sharpness"). To that extent 4x the image information present is 4x the resolution.

The notion of what a display's resolution is has been established for years and years.

We've been around and around this. If you wish to reinvent that concept of a display's resolution, then go ahead. But it will be an uphill battle for you. I wouldn't regard it as worth it.
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Old 11-09-2014, 07:37 AM
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Look, I'm done here. This is silly.

V/I is futile.
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Old 08-09-2015, 06:46 AM
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Originally Posted by KidHorn View Post
Quote:Originally Posted by tgm1024 

No, again:  Imagine 100x100 vs 200x100 displays (note, 100 pixels high in both cases, same physical size).  People will perceive twice the information in the 2nd display.

Has anyone ever done this? Doubling one resolution and not the other. How can you say with any certainty how people would perceive that? My guess is the image would look more distorted instead of sharper.


In the center, "full" resolution. On the left, full horizontal resolution but 1/2 vertical resolution. On the right, 1/2 resolution for both axes.


Also, Nikon's D1X (2001) DSLR had pixels that were twice as high as they were wide.

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Old 08-09-2015, 08:12 AM
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Look, I'm done here. This is silly.
It's no sillier than pondering whether a 24" cube is twice the size of a 12" cube, or if it's eight times larger.

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Old 08-11-2015, 06:09 PM
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I think I can throw another concept in the mix that might clarify this - visual accuity as measured in arcminutes (or arc seconds). As in like, degrees-minutes-seconds. This is essentially the fraction of our visual field that an element takes up. Its measured in angles, which would be a linear/1 dimensional measurement, which can be translated into other things if we specify a fixed viewing distance. Essentially, if we can halve the amount of our vision an object takes up (pixel, scircle of light, tip of a needle, drop of ink on paper, whatever), then we can use a collection of those to represent an image with twice as much detail.

A screen with 1 arcminute big pixels relative to our viewing position is half as sharp as a screen with .5 arcminute pixels, because we can resolve something half the linear size. Thats been pretty well accepted by the photography/print world for a while.

Another similar concept is lines of resolution - its relevant on analog CRT displays where a display with 800 lines of resolution is going to be twice as sharp as a display with 400 lines of resolution. With square or square-ish pixels, you don't get 4 times more detail with 2x more lines of resolution.

I realized this is just rehashing some other things people have said but with different ways of measuring it, but it shows that resolution has been commonly measured in terms of a linear, 1 dimensional factor. Think of it like the circumference of a circle, a circle is a two dimensional object, but if you double the circumference, the circle will appear twice as big, not 4x bigger. Heck, we even measure our screen sizes in diagonal - nobody is going to brag how their 60" tv is 4x the size of a 30" tv, because thats just not how we perceive images. Yes, it does have 4x the area and thus takes 4x more raw material to make, but its not 4x bigger.

I think the same confusion started happening with digital images initially with camera megapixels (mentioned before but I'll elaborate on this too). The common pro advice on digital camera resolution was "Don't worry about megapixel counts - an 8 megapixel camera isn't twice as sharp as a 4 megapixel camera, its only 1.5x sharper but megapixel is an easier way to inflate the apparent specs." I realize the same advice was also given to emphasise that other things matter like lens quality, dynamic range, noise, color quality, etc, but I pretty clearly remember articles being written about how megapixel counts are nonsense because it look like theres a bigger difference in sensor resolution than there really is.

Long story short, we don't count pixels, but our vision works based on the apparent size of tiny circles of light and the smaller you can make the radius of those circles of light, the sharper it'll be. In the digital world, it means you do need to divide the area of a pixel by 4 to fit in twice as many pixels in each dimension, but perceived resolution is most definitely proportional to that linear resolution while assuming that its shrunk equally in both directions.

The 200x100 image with 2:1 pixel ratio didn't really resonate with me - it only has double the pixels, but it also has either "exactly the same resolution" or "double the resolution" depending on which way its measured. You really need to keep the pixel aspect ratio constant to make an apples to apples comparison of resolutions. 200x200 is definitely twice as sharp as 100x100, but a weird 2:1 pixel ratio display is only better on, for example, old computers because it gave you extra pixels to use for dithering. If you've ever played any game in monochrome hercules graphics on an old system, that has 640x200 resolution, so they could get dither the heck out of it horizontally with not too awful results despite the monochrome 1 bit display, and they could make text sharper too relative to 320x200 CGA graphics.

Its still true that 4k has 4x the pixels of 2k (1080p), but you will only perceive it to be twice as sharp at best.
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Old 08-12-2015, 05:20 AM
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Originally Posted by Pitot Static View Post
...
The 200x100 image with 2:1 pixel ratio didn't really resonate with me - it only has double the pixels, but it also has either "exactly the same resolution" or "double the resolution" depending on which way its measured. You really need to keep the pixel aspect ratio constant to make an apples to apples comparison of resolutions. 200x200 is definitely twice as sharp as 100x100, but a weird 2:1 pixel ratio display is only better on, for example, old computers because it gave you extra pixels to use for dithering. If you've ever played any game in monochrome hercules graphics on an old system, that has 640x200 resolution, so they could get dither the heck out of it horizontally with not too awful results despite the monochrome 1 bit display, and they could make text sharper too relative to 320x200 CGA graphics.

Its still true that 4k has 4x the pixels of 2k (1080p), but you will only perceive it to be twice as sharp at best.
If you had a 200x100 pixel display - which could be a 2:1 pixel aspect ratio or it could (in theory) be a display with square pixels but with quite big gaps pixels on one axis. If you take the total resolution of the display to be the total number of pixels on the entire display, it won't matter which way the display is rotated, it will always have the same total resolution. A normal 1.78:1 "4K" (3.84K) TV will have the potential (assuming the viewer is close enough/has good enough eyesight) to enable people to resolve 4x as many objects in the same space as the same size 1080p TV. Wouldn't 4x the objects (or pixels) resolved be 4x the (total) resolution?

Surely it's similar with image capture devices - all things being equal it's the total number of sensors that will give you the total resolution (or maximum captured spatial resolution) of the capture device (assuming nothing else is limiting it). Sensors on the capture device or pixels on a display - no matter how arranged (whether square with no gaps or non-square or square with gaps or hexagonal, or whether it's just a few sensors/pixels randomly added) - or rods/cones in the eye, surely the total number of pixels (or sensors) is what gives the total resolution of the system (and unlike just counting the pixels across, this would be true even for different image aspect ratios, different pixel aspect ratios or the other ways mentioned, including rotating of the display/capture device).

Note: This is not talking about "sharpness" and is only talking about resolution (eg. total (spatial) resolution of a display) in pixels (and ignoring other things like blur and other things which reduce the true displayed resolution).
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Old 08-12-2015, 06:00 AM
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Holy thread resurrection batman!

This is an easy one; humans don't have much of an eye for area, its hard to quickly judge the size of an area, or even relative size. Length is much easier, we can all do that. Thus, even if an object's function depends on the size of its area, we are still likely to refer to it by length in one dimension.

The TV is a perfect example, its function depends upon the AREA of the screen and the number of pixels, both 2 dimensional measurements. The only reason we are able to refer to a TV's size by diagonal length and not area is that the aspect ratio is always constant for every TV. This also breaks our comparisons for relative size (for anyone who doesn't properly understand length vs area anyway).

So most people might refer to a 60" TV as double the size of a 30" TV, because 2x30 = 60 right? Wrong. Those numbers are lengths, the size of a TV is an area, area = (length)^2, (2)^2 = 4 so a 60" TV is 4 times the size of a 30" TV.

Its exactly the same with resolution. Yes if you double only the vertical resolution, then you have twice the resolution. But if you double both vertical and horizontal resolution (which is what happens going from 1080p -> 2160p), then you have 4x the resolution, 4x the detail and 4x the sharpness (assuming perfect eyesight). How has this arguement raged for 5 dozen posts? Seriously?

And if you want to bring the visual accuity rhetoric that's fine, just be aware it only applies to static images, as soon as
there's motion its all irrelevant.
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Old 08-12-2015, 07:17 AM
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Originally Posted by Ormy View Post
Holy thread resurrection batman!

This is an easy one; humans don't have much of an eye for area, its hard to quickly judge the size of an area, or even relative size. Length is much easier, we can all do that. Thus, even if an object's function depends on the size of its area, we are still likely to refer to it by length in one dimension.

The TV is a perfect example, its function depends upon the AREA of the screen and the number of pixels, both 2 dimensional measurements. The only reason we are able to refer to a TV's size by diagonal length and not area is that the aspect ratio is always constant for every TV. This also breaks our comparisons for relative size (for anyone who doesn't properly understand length vs area anyway).

So most people might refer to a 60" TV as double the size of a 30" TV, because 2x30 = 60 right? Wrong. Those numbers are lengths, the size of a TV is an area, area = (length)^2, (2)^2 = 4 so a 60" TV is 4 times the size of a 30" TV.

Its exactly the same with resolution. Yes if you double only the vertical resolution, then you have twice the resolution. But if you double both vertical and horizontal resolution (which is what happens going from 1080p -> 2160p), then you have 4x the resolution, 4x the detail and 4x the sharpness (assuming perfect eyesight). How has this arguement raged for 5 dozen posts? Seriously?

And if you want to bring the visual accuity rhetoric that's fine, just be aware it only applies to static images, as soon as
there's motion its all irrelevant.
How much more of your field of view does a 60" tv take up than a 30"?

Ask anyone you know in real life whether a 60" tv is four times bigger or two times bigger than a 30"?

You won't have any trouble convincing them that it has 4x the area, but the apparent size is proportional to the linear dimensions, not the area. And if you throw "What if the 60" diagonal tv has a 2:1 ratio and the 30" tv has a 1:1 ratio" into the mix, people will just get confused. We're talking about 16:9 displays with square pixels here, a 2:1 screen ratio or 2:1 pixel ratio doesn't really fit into the conversation. It distracts from the original debate of "Do we perceive sharpness based on pixel count in two dimensions or one dimension?" The answer is: 1 dimension. The radius of the smallest thing your eye can see needs to be halved to double the detail. The fact that you have to put 4 pixels in the space of one to double that detail is a side effect of the fact that the display is two dimensions, but not a requirement of human visual accuity to count ALL the pixels that take up the display and not just one dimension (then apply the fact that its square pixels and a constant screen ratio).

4k is 4x more pixels. 4k is twice as sharp.
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Old 08-12-2015, 07:30 AM
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It distracts from the original debate of "Do we perceive sharpness based on pixel count in two dimensions or one dimension?"
The thread isn't about perceived sharpness. The original poster didn't ask the above. It's about how much resolution a "4K" (3.84K) display is actually displaying (or could display) compared to a 1080p TV.

Quote:
We're talking about 16:9 displays with square pixels here, a 2:1 screen ratio or 2:1 pixel ratio doesn't really fit into the conversation
This is because your formula doesn't work when those are changed. But they (eg. screen aspect, pixel aspect etc.) can be changed/different. A resolution figure (total resolution) that allows them to change is the more correct answer. See above - with your formula if you rotated the TV 90 degrees the total (spatial) resolution is different - but really the total resolution the TV is displaying hasn't changed at all - you just need to take all the pixels into account - not just the width in pixels.

edit: I suppose you could also measure it in cycles/line pairs or tv lines per picture height - and in that sense it wouldn't quadruple.

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Old 08-13-2015, 03:25 PM
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Out don't know, but i've read this whole thread. And still, I keep coming to the same conclusion with basic mathematics telling me 2160p is 2X greater resolution than 1080p.

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Old 08-13-2015, 03:46 PM
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Out don't know, but i've read this whole thread. And still, I keep coming to the same conclusion with basic mathematics telling me 2160p is 2X greater resolution than 1080p.
But what is (3840x2160)/(1920x1080) since a TV doesn't have just one dimension?

Also, how much (total) resolution would a 5120x2160p TV be compared to a 3840x2160p TV? Is a 5120x2160p TV exactly the same resolution as a 3840x2160p TV or is it more (assume for this it could receive and display content in that format)?

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Old 08-13-2015, 05:28 PM
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But what is (3840x2160)/(1920x1080) since a TV doesn't have just one dimension?

Also, how much (total) resolution would a 5120x2160p TV be compared to a 3840x2160p TV? Is a 5120x2160p TV exactly the same resolution as a 3840x2160p TV or is it more (assume for this it could receive and display content in that format)?


F'N A, I don't know. What really is High Definition by definition? Hell, did everyone back in 2004 consider 720p 2/3HD? To make matters worse, 1080p can't be considered Full HD anymore now can it?

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