Pixel question - AVS | Home Theater Discussions And Reviews
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post #1 of 10 Old 01-29-2014, 04:02 PM - Thread Starter
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Hello all, a quick question in regards to the size of pixels. Is there a difference in the size of a pixel of a 60 inch TV or a 32 inch TV? I was thinking that the pixels are the same and that there would be more pixels in one line of resolution. My child says that the pixels are smaller on a smaller set and larger pixels on larger set. Thanks in advance for your replies, Pete
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post #2 of 10 Old 01-29-2014, 04:47 PM
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In general a bigger screen has bigger pixels but as you can see here that is not always the case. You can conclude from these comparisons that a 60'' will have bigger pixels than a 32''.
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post #3 of 10 Old 01-29-2014, 06:52 PM
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Life seems to always be more complicated than one first presupposes.

 

The distance from pixel center to pixel center (which I think is what you are asking) depends on both the resolution and screen size, and that is after we assume the TV has a 16:9 aspect ratio, pixels laid out in a square arrangement (as many pixels per inch horizontal as per inch vertical, typical of modern LCD screens).

 

Diagonal Size

(inches)

Designation

Lines of

Resolution

Width

(inches)

Height

(inches)

Inches from

pixel center

to

pixel center

32 32" Enhanced definition (480p) 480 27.89 15.67 0.033
32 32" HD (720p) 720 27.89 15.67 0.022
32 32" HD (many 720p TVs are natively 768) 768 27.89 15.67 0.020
32 32" "Full HD" 1080 27.89 15.67 0.014
60 60"  HD 720 52.31 29.39 0.041
60 60" "Full HD" 1080 52.31 29.39 0.027
60 60" "4K" UHD 2160 52.31 29.39 0.014

 

You may notice that as the screen size goes up for a given resolution, the distance from pixel center to pixel center goes up. On the other hand, for a given screen size, as the resolution goes up, the distance from pixel center to pixel center goes down.

 

Then, in just rough terms, a large TV is generally sold at a higher resolution than a small TV; e.g., you may find it hard to impossible to find a 60-in 720p TV but rather find the vast majority of 60-in TVs are 1080p; but "720p" or more likely 768 native is probably more common than other resolutions in the 32-in size.

 

So, screen size alone really doesn't give enough information.

 

I don't want to say "pixel distance" because that has a technical meaning (the gap between a pair of adjacent pixels), nor do I want to say "pixel size" (the size of the part that emits light or lets the light through).

 

My own numbers: bedroom TV is "720p" but has a native screen resolution of 768p, so there is 0.020 inches between pixel center to the next pixel center. My big TV is 50", resulting in 0.023 inches between pixel center to pixel center. 0.020 and 0.023 are fairly close, but the larger TV is also more expensive, both because physical size and because of the higher native resolution (more than twice the number of total pixels).


My very humble setup:
Man Cave:Vizio E500i-A1 "Smart TV" (50-in 1080p 120Hz LED/LCD, has Netflix app.), Sony BDP-S3100 Blu-ray player, Roku N1000 (original model), PC (Windows 7), Comcast Internet (110Mbps/12Mbps).
Bedroom:LG 32LV3400-UA TV (32-in 768p 60Hz LED/LCD), HD DVR (Motorola RNG200N), Xfinity Comcast cable (Digital Preferred Plus), DVD/VHS player.
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post #4 of 10 Old 01-30-2014, 01:08 AM - Thread Starter
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Thank you all for your replies. The reason for the question was because my 12 year old a/v enthusiast and I were in best buy talking about this topic. A random guy said I was wrong, he was an engineer, and then he left. I thought a pixel was pretty much the same size and that to make a larger display, more pixels were added to the lines of resolution to make the size necessary. It seems like pixels sizes vary based on the above posts. I would then ask if a pixel is small in, say, my iPhone, then those same tiny pixels could be made in a tv panel on a large scale and a tv could look like a 8k since the pixels would be so small. I am I missing something? Thx Pete
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post #5 of 10 Old 01-30-2014, 03:07 AM
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If you have a 1080p display, it has 1920 pixels horizontally and 1080 pixels vertically regardless of its size, so yes, the size of the pixels will be different depending on the size of the display.
Something like your iPhone will have much smaller pixels than a 60" 1080p TV

An iPhone 5s is 326 pixels per inch, and a 60" 1080p display is only 37 PPI.
You may find this site useful: http://www.sven.de/dpi/
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post #6 of 10 Old 01-30-2014, 06:31 AM
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Quote:
Originally Posted by pete6737 View Post

Thank you all for your replies. The reason for the question was because my 12 year old a/v enthusiast and I were in best buy talking about this topic. A random guy said I was wrong, he was an engineer, and then he left. I thought a pixel was pretty much the same size and that to make a larger display, more pixels were added to the lines of resolution to make the size necessary. It seems like pixels sizes vary based on the above posts. I would then ask if a pixel is small in, say, my iPhone, then those same tiny pixels could be made in a tv panel on a large scale and a tv could look like a 8k since the pixels would be so small. I am I missing something? Thx Pete

It's very difficult to make a large display with tiny pixels like on your phone. It can be done, at least in theory, but with a lot of failed attempts.
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post #7 of 10 Old 01-30-2014, 12:57 PM
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Originally Posted by KidHorn View Post

It's very difficult to make a large display with tiny pixels like on your phone. It can be done, at least in theory, but with a lot of failed attempts.

Why do you say that? I'm not sure that is correct.

Your reference to 'a lot of failed attempts' suggests a low yield, and that as the number of pixels increases, the likelihood to have 100% of the pixels working on a panel without defect goes down. This is true, but it is a second-order effect - defect density is a function of surface area, so the larger the panel, the greater the probability of a defect (independent of pixel size). This means that a 60" 1080p panel has about 4 times the probability of containing defects than a 30" 1080p panel regardless of the fact that the pixels on the 60" panel are 4 times bigger. And it also means that a 60" 4K (2160p) panel has about the same probability of having defects as the 60" 1080p panel regardless of the fact that it contains 4 ties the number of pixels and they are smaller.

The second order aspect has to do with the size of the defects and their impact. Some 'defects' are so small that the pixel can function properly despite the fact that it contains a 'defect'. When everything shrinks, the possibility of the electronics within a pixel to function properly despite the presence of a small defect shrinks with it. So from that point of view, yield loss on panels using smaller pixels will be higher than yield loss on panels using larger pixels...

The focus in the manufacturing plant is to minimize/reduce/eliminate the possibility of defects of any size, and this effort will benefit the yields of small-pixel and large-pixel panels about equally.

The fundamental thing that does change when manufacturing a larger panel with smaller pixels is the electronic load and the demands on the drive electronics. As signal lines get longer they become harder to drive. And as signal lines have more transistors/pixels attached to them they become harder to drive. So a 60" panel with pixels the size of your iPhone 5s would have over 17,000 pixels across each line of the display, representing a much. much more difficult line to drive than a 60" 1080p panel with 'only' 1920 pixels. There would be no way to drive that 'iPhone-like' panel quickly enough to get any kind of video out of it (or even a still image - the panel would probably begin to lose it's image before a full refresh could be completed).

So sorry for the long-winded response, but I believe the primary problem with using small pixels on large panels is associated with the engineering challenge of maintaining the necessary signal timing to refresh at 30 or 60 frames per second, and issues associated with increased yield loss (or 'lots of failed attempts') are secondary...

-fafrd
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post #8 of 10 Old 01-30-2014, 01:25 PM
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Originally Posted by fafrd View Post

Why do you say that? I'm not sure that is correct.

I say that because that's been the production history of every panel or integrated circuit ever made. The larger the die and/or the more components you try to put on a die, the greater the failure rate. Not only is it common sense, it's been proven true countless times.
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post #9 of 10 Old 01-30-2014, 02:53 PM
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Quote:
Originally Posted by KidHorn View Post


I say that because that's been the production history of every panel or integrated circuit ever made. The larger the die, the greater the failure rate. Not only is it common sense, it's been proven true countless times.

You and I are perfectly aligned in terms of this statement.
Quote:
Originally Posted by KidHorn View Post

I say that because that's been the production history of every panel or integrated circuit ever made. The more components you try to put on a die, the greater the failure rate. Not only is it common sense, it's been proven true countless times.

And on this statement we are not perfectly aligned. While it is true that putting more components on the same size die will result in a higher 'failure rate' (yield loss) because of the increased sensitivity to failure in the face of the smallest class of defects, this effect is second-order and far, far smaller than the loss of yield resulting from increased die size...

-fafrd
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post #10 of 10 Old 01-31-2014, 06:10 AM
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Quote:
Originally Posted by fafrd View Post


And on this statement we are not perfectly aligned. While it is true that putting more components on the same size die will result in a higher 'failure rate' (yield loss) because of the increased sensitivity to failure in the face of the smallest class of defects, this effect is second-order and far, far smaller than the loss of yield resulting from increased die size...

-fafrd

Why don't you read up on microprocessor manufacturing. Intel follows a tick tock manufacturing paradigm. They start out with a certain processor with larger components, then after they improve their manufacturing, they produce basically the same thing with smaller components. Yield is a function of die size and complexity. I'm not sure what you mean by second order, but both play a big role.

http://www.intel.com/content/www/us/en/silicon-innovations/intel-tick-tock-model-general.html
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