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How Does Screen Resolution Work?

Last response: in Graphics & Displays
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July 30, 2011 5:06:39 AM

Hello everyone,

I am sure this is a simple answer, yet it has always baffled me.

I have a 1920x1080 display on my notebook. If I change it to a lower resolution, like 1680x1050, where do all the pixels go? I do not understand how it works at all. Do the pixels somehow get bigger? Though this seems like it would not make sense, because a pixel is hardware, how can the size be changed?

Then, when I set my notebook to a very low resolution, like 800x600, black bars appear on each side of the screen. This does not happen with higher resolutions like, say, 1680x1050. Why is this?

Thank you!

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a b Î Nvidia
July 30, 2011 5:21:46 AM

On CRT screens it would actually change the resolution but you are correct about LCDs; they are made up of a certain number of physical pixels.
Your computer can be set to change the resolution in two different ways. It can either stretch the image to fill the screen or use black bars like you mention. So if you set a 1920x1080 screen to 1680x1050 you will end up with bars 15 pixels wide on the top and bottom and 120 pixels each on the sides. If your system is set to fill the screen(usually the default) then the card will do it's best to do so. This means that you will get some doubled pixels which cause minor image distortion/blurriness if you look close enough. It's usually easiest to notice on something like small text. Here is an example of running 800x600 on a 1024x768 screen:
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July 30, 2011 5:35:09 AM

Best answer selected by shfiftyfive.
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July 30, 2011 5:35:53 AM

jyjjy said:
On CRT screens it would actually change the resolution but you are correct about LCDs; they are made up of a certain number of physical pixels.
Your computer can be set to change the resolution in two different ways. It can either stretch the image to fill the screen or use black bars like you mention. So if you set a 1920x1080 screen to 1680x1050 you will end up with bars 15 pixels wide on the top and bottom and 120 pixels each on the sides. If your system is set to fill the screen(usually the default) then the card will do it's best to do so. This means that you will get some doubled pixels which cause minor image distortion/blurriness if you look close enough. It's usually easiest to notice on something like small text. Here is an example of running 800x600 on a 1024x768 screen:
http://upload.wikimedia.org/wikipedia/en/f/f7/Native-resolution_800x600_on_1024x768.JPG

Thank you very much for your thoughtful answer. That makes perfect sense. It is a task that can only be solved in an imperfect manor. Thank you!
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a b Î Nvidia
July 30, 2011 5:44:22 AM

A LCD screen has a fixed number of pixels. It never changes. Text and graphics look the sharpest when you are using the LCD screen at it's native (maximum) resolution.

When you lower the resolution, text will look larger, but they can look a bit fuzzy. This is because something called interpolation is used to best estimate how text and graphics will be displayed on the screen at lower resolution. Basically the greater the difference between native resolution and the lower resolution used, the greater the "fuzziness" can be.

The following are examples of text display on a 1920x1080 resolution monitor at various resolutions:












The reason why there are black bars when you set the resolution to 800x600 is because that aspect ratio is 4:3 vs. an aspect ratio of 16:9 at the monitor's native resolution. This is done so that the text and images do not appear stretched across the screen if the black bar were not there.

1680x1050 most likely has very thin black bars on top and bottom to maintain the correct aspect ratio of 16:10. Since your screen is 1920x1080, the horizontal black bars are only 15 pixel wide on the top and bottom of the screen.
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a b Î Nvidia
July 30, 2011 6:17:21 AM

jaguarskx said:
The reason why there are black bars when you set the resolution to 800x600 is because that aspect ratio is 4:3 vs. an aspect ratio of 16:9 at the monitor's native resolution. This is done so that the text and images do not appear stretched across the screen if the black bar were not there.

1680x1050 most likely has very thin black bars on top and bottom to maintain the correct aspect ratio of 16:10. Since your screen is 1920x1080, the horizontal black bars are only 15 pixel wide on the top and bottom of the screen.

Yeah, the above is true as well. Even if you are stretching the aspect ratio will still be maintained causing black bars as well if it doesn't match the native aspect ratio.
I believe the bars would be wider than that with 1680x1050 on a 1920x1080 screen though and on the sides, not the top and bottom. The 1050 would be stretched to 1080(adding 30 pixels.) 1080 at 16:10 would be 1728 x 1080 which would be bars on the sides of 96 pixels each. To match the aspect ratio(no bars) you would want to use 1600x900.
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a c 172 Î Nvidia
July 30, 2011 1:49:28 PM

This topic has been closed by Mousemonkey
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