Screen resolution, dpi, and monitor settings.

So I understand the basic properties of resoultion and dpi, but what is going on when i keep my resolution the same, but change the dpi in my display tab? Then how does changing the screen size via the buttons on the monitor complicate resolution and dpi? I thought i had all this down until i really thought about it, my monitor only has a set amount of pixels, so if i set my screen resolution to the max, the dpi would be a set number and a variable like it is in reality, and i shouldnt be able to resize the screen or i would lose pixels because they a pixel is a set size. Can someone make sense of all this confusion for me?

 

Changing the DPI is just a feature in the operating system that tells it to make everything (the Start Button, the text, the desktop icons, etc.) bigger. Lowering the resolution can have the same effect (it makes everything bigger), but then you have to run outside of the native resolution, which makes everything blurry and that's no good.

Another way to look at it: For simplicity's sake, let's say the Vista Start Button is exactly 96 pixels. The standard DPI for Windows is 96 DPI, meaning the start button takes up 96 of your LCD's physical pixels. If we increase the DPI to 120, Windows increases the size of the Start Button to take up 120 physical pixels on your screen. The buttons (and everything else) are bigger, but you're still running at native resolution.

Increasing the DPI is just a smarter way of making everything bigger. This is especially helpful in my case (17" WUXGA), so I can make stuff readable without having to run outside of my LCD's native res.

 

I assume you are referring to LCD panels.

Each panel is formed of a fixed number of pixels, for example 1280 wide and 800 high for WXGA. The display will be sharpest at this resolution. You can use the panel at a lower resolution but the display will get fuzzy because there is interpolation to convert from the logical resolution to the physical resolution.

The DPI setting is another parameter which changes overall scaling. The default setting is 96 DPI and most current desktop displays use this. For example, 17" 1280 x 1024 is 96.4 pixels per inch. When the display PDI and Windows DPI are the same then you will get fonts being displayed at their correct size. However, in order to get more detail onto a notebook screen, people have moved to more and smaller pixels. For example, 15.4" 1680 x 1050 is 128 pixels per inch. If Windows uses the standard 96 DPI setting then everything is displayed smaller. If you change the Windows DPI to match the display pixels per inch then the text should be the correct size.

So much for the theory. The reality is that formatting tends to fall apart when you move away from 96 DPI. Web browsers tend to do whatever they want, while windows and dialog boxes still have their sizes calculated assuming 96 DPI so text gets bigger but the box does not. Last year's information about Vista was that it was going to fix this mess and it was the feature I was most looking forward to. However, it isn't there and Vista handles this mess no better than XP. It shouldn't be impossible to have higher resolution displays for better quality while maintaining the correct size of what is displayed.

Have I managed to clarify this or confuse you further?

John

 

Both of the posts are great! Thanks.

So if i understand this correctly, changing the dpi doesn't actually change the dpi, it just adds pixels to the icons and junk right?

If i am correct on that, then the resolution and dpi makes perfect sense to me, but what about when i squish the screen together with the buttons on the monitor? It cannot possibly change the number of pixels, so does that mean it essentially works the same as changing the screen resolution away from native resolution? I mean, with interpolation and junk.

And lastly, if my understanding above is correct, is there a way for windows to know the number of pixels my computer has, set native resolution, and align the screen up perfectly so there is no interpolation?

 

Like they said, maybe sometime in the past dpi actually meant "dots per inch", but these days it's just a ratio for how many pixels your OS uses for certain things like fonts.

(edit) It sounds like you're using a VGA connection with an LCD. There are technologies that are supposed to do what you're describing, but I've only had mixed luck with them. I have yet to get a really good image out of my HEL80, on an external monitor.