Perplexed by pixels
May 16, 2022 1:32 PM Subscribe
Is it fair to say that a resolution of 1280 x 1024 has twice as many pixels as a resolution 640 x 512?
Wouldn't it be four times as many? A 2 x 2 resolution has four pixels, but a 4 x 4 has sixteen.
posted by box at 1:38 PM on May 16, 2022
posted by box at 1:38 PM on May 16, 2022
Agree. It would be four times as many. Doubling the length doubled the pixels, doubling the width doubled it again.
posted by DirtyOldTown at 1:39 PM on May 16, 2022 [1 favorite]
posted by DirtyOldTown at 1:39 PM on May 16, 2022 [1 favorite]
You doubled both the length and width - if x * y = xy. 2x * 2y = 4xy
1280 x 1024 has a resolution of 1,310,720 pixels
640* 512 has a resolution of 327,680
So, the first divided by the second = 4 (not 2)
posted by metahawk at 1:42 PM on May 16, 2022
1280 x 1024 has a resolution of 1,310,720 pixels
640* 512 has a resolution of 327,680
So, the first divided by the second = 4 (not 2)
posted by metahawk at 1:42 PM on May 16, 2022
It's easier to understand with smaller numbers. Say you have a rectangle that's 1x2. Easy, that's an area of 2. Then you have a 2x4 rectangle, where each side is twice the length of the sides in the first rectangle. The area of that one is 8. Do it again to get a rectangle that's 4x8. That's 32. Likewise, 1x3=3, 2x6=12, 4x12=48.
posted by kevinbelt at 1:54 PM on May 16, 2022 [1 favorite]
posted by kevinbelt at 1:54 PM on May 16, 2022 [1 favorite]
One thing that may be confusing is that video resolution is often referred to by only one dimension. HD video is 1920 × 1080 (just over 2 million pixels) but the industry jargon for it is 2K because the one dimension is approximately 2000. 4K video (sometimes called UHD) is 3840 × 2160 (over 8 million pixels). 4K has four times the resolution of 2K video and not just twice as much as you might expect based on the names.
posted by fedward at 1:57 PM on May 16, 2022
posted by fedward at 1:57 PM on May 16, 2022
It has 4 times as many pixels, but it has twice the resolution.
posted by hydra77 at 2:32 PM on May 16, 2022 [7 favorites]
posted by hydra77 at 2:32 PM on May 16, 2022 [7 favorites]
Yes certainly 4 times the pixels literally speaking. That much is certain.
As hydra77 alludes to however there are looser terms for this kind of thing that are more or less intuitive. If I asked a video professional to double or halve the resolution of an image, they would understand that I wanted both the horizontal and vertical resolutions to be included. To change only one of them would distort or crop the image. Yet the process of doubling or halving both dimensions is to quadruple or quarter the pixel data they encompass.
It can be confusing so it's good to make sure you are using the right terms. Colloquially you could correctly say that the larger one is twice the resolution of the smaller, or that it has twice the fidelity, since in terms of resolving detail, it's twice as good. But it is also correct to say that it is four times the pixels, the data, the bandwidth etc.
Just as you can say a pipe is "twice as wide" as another but that implies considerably more than twice the water can travel through it.
posted by BlackLeotardFront at 2:39 PM on May 16, 2022 [2 favorites]
As hydra77 alludes to however there are looser terms for this kind of thing that are more or less intuitive. If I asked a video professional to double or halve the resolution of an image, they would understand that I wanted both the horizontal and vertical resolutions to be included. To change only one of them would distort or crop the image. Yet the process of doubling or halving both dimensions is to quadruple or quarter the pixel data they encompass.
It can be confusing so it's good to make sure you are using the right terms. Colloquially you could correctly say that the larger one is twice the resolution of the smaller, or that it has twice the fidelity, since in terms of resolving detail, it's twice as good. But it is also correct to say that it is four times the pixels, the data, the bandwidth etc.
Just as you can say a pipe is "twice as wide" as another but that implies considerably more than twice the water can travel through it.
posted by BlackLeotardFront at 2:39 PM on May 16, 2022 [2 favorites]
Yes. Twice the 2D resolution (twice as many x-pixels and twice as many y-pixels) same aspect ratio
posted by Dub at 5:43 PM on May 16, 2022
posted by Dub at 5:43 PM on May 16, 2022
1280 x 1024 has a resolution of 1,310,720 pixels
640* 512 has a resolution of 327,680
Unfortunately, terminology around these topics gets super sloppy and it's often quite hard to work out what people intend their words to mean.
The way I use them and see them used most often, "resolution" refers to the number of distinct items that can be represented inside a specific amount of linear distance. It's a term that came to us from printing, and in that context its customary units are dots per inch (dpi). The first consumer-oriented laser printer - the one that introduced Adobe and its PostScript printing language to the wider world - was the Apple Laserwriter, and its print resolution was 300dpi.
Resolution in this sense also gets applied to display screens, and in that context it generally refers to the number of pixels that fit within a specific linear distance. For many years, largely due to the inability of the text rendering subsystem inside Microsoft Windows to work properly with anything finer, the usual display screen resolution was nominally 96dpi. The first display screens that most people will have encountered featuring finer resolution than that were the ones on Apple's first "retina" iPhones, which if I recall correctly were 288dpi.
Resolutions of around 300dpi or better, at the kinds of viewing distances typical for paper or display screens, correspond pretty well to that of the human eye. There's not a huge amount of point in designing stuff finer than that, because you rapidly run into diminishing returns; a 600dpi image will look a little bit better than a 300dpi one to most people, but you'd have to be examining them fairly closely to see the difference. In general, 300dpi is roughly where properly rendered, nicely anti-aliased pixels stop being perceived as noticeably jagged by most people.
But there's a second sense for the word "resolution", where it refers not so much to fineness of detail as to the total amount of detail representable by an image and/or display device. That's where you see total pixel counts quoted, like 640x512 or 3840x2160. The first figure is always the horizontal pixel count and the second is vertical.
Confusingly, that measurement is sometimes also named "size", but that's more often and more correctly used to talk about how physically big things really are. The industry standard measure for size, in the context of display screens, is taken along the diagonal of the active viewing area, which makes the relationship between size, pixel count and resolution a little complicated.
If we start by assuming that pixels are square (by no means a safe assumption in the context of digital video encoding, but let's not even go there today; display screens with physically non-square pixels are quite rare) then 1280x1024 pixel display is going to be 1280 / 1024 = 1.25 times as wide as high; that's the display's "aspect ratio".
Applying Pythagoras's theorem to derive the relationship between diagonal measurement and height, we can calculate that the diagonal is going to be √(1.252 + 12) = 1.6 times the height. The height of 1024 pixels at 96dpi will be 1024 / 96 = 10.67 inches, which means that the diagonal will be 1.6 × 10.67 = 17 inches. So a screen with that resolution and those pixel counts would be sold as a 17 inch display.
That's pretty much all the maths you'll need to get comfortable with in order to make sense of most of what gets talked about around these topics.
posted by flabdablet at 10:47 PM on May 16, 2022
640* 512 has a resolution of 327,680
Unfortunately, terminology around these topics gets super sloppy and it's often quite hard to work out what people intend their words to mean.
The way I use them and see them used most often, "resolution" refers to the number of distinct items that can be represented inside a specific amount of linear distance. It's a term that came to us from printing, and in that context its customary units are dots per inch (dpi). The first consumer-oriented laser printer - the one that introduced Adobe and its PostScript printing language to the wider world - was the Apple Laserwriter, and its print resolution was 300dpi.
Resolution in this sense also gets applied to display screens, and in that context it generally refers to the number of pixels that fit within a specific linear distance. For many years, largely due to the inability of the text rendering subsystem inside Microsoft Windows to work properly with anything finer, the usual display screen resolution was nominally 96dpi. The first display screens that most people will have encountered featuring finer resolution than that were the ones on Apple's first "retina" iPhones, which if I recall correctly were 288dpi.
Resolutions of around 300dpi or better, at the kinds of viewing distances typical for paper or display screens, correspond pretty well to that of the human eye. There's not a huge amount of point in designing stuff finer than that, because you rapidly run into diminishing returns; a 600dpi image will look a little bit better than a 300dpi one to most people, but you'd have to be examining them fairly closely to see the difference. In general, 300dpi is roughly where properly rendered, nicely anti-aliased pixels stop being perceived as noticeably jagged by most people.
But there's a second sense for the word "resolution", where it refers not so much to fineness of detail as to the total amount of detail representable by an image and/or display device. That's where you see total pixel counts quoted, like 640x512 or 3840x2160. The first figure is always the horizontal pixel count and the second is vertical.
Confusingly, that measurement is sometimes also named "size", but that's more often and more correctly used to talk about how physically big things really are. The industry standard measure for size, in the context of display screens, is taken along the diagonal of the active viewing area, which makes the relationship between size, pixel count and resolution a little complicated.
If we start by assuming that pixels are square (by no means a safe assumption in the context of digital video encoding, but let's not even go there today; display screens with physically non-square pixels are quite rare) then 1280x1024 pixel display is going to be 1280 / 1024 = 1.25 times as wide as high; that's the display's "aspect ratio".
Applying Pythagoras's theorem to derive the relationship between diagonal measurement and height, we can calculate that the diagonal is going to be √(1.252 + 12) = 1.6 times the height. The height of 1024 pixels at 96dpi will be 1024 / 96 = 10.67 inches, which means that the diagonal will be 1.6 × 10.67 = 17 inches. So a screen with that resolution and those pixel counts would be sold as a 17 inch display.
That's pretty much all the maths you'll need to get comfortable with in order to make sense of most of what gets talked about around these topics.
posted by flabdablet at 10:47 PM on May 16, 2022
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Another way to consider it is the total number of pixels of 1280x1024 is: Because multiplication is commutative (the order doesn't matter) you can again rewrite that as: Since 2*2 is 4, the answer is clearly 4 times as many pixes as 640 x 512 .
posted by nobeagle at 1:38 PM on May 16, 2022 [12 favorites]