DPI Confusion

[oscarse]

Can someone Please explain what is going on with the DPI settings in XP?

I have a screen that is supposed to be 1680 x 1050 pixels with a screen that is roughly 13" x 8.25" ... this works out to be about 130 pixels per inch

I read 96dpi as being 96 dots per inch

The advanced screen settings 120dpi suggests 125% size enlargement (which seems to be the result but it doesn't make any sense that increasing the dpi should make an image larger)

This is where my mind is confused ... if I have an image that is 50 dots wide and I view it at 96dpi I expect it would be larger then if I viewed the same image at 120dpi

Why is something this simple so confusing?

 

[Nelviticus]

The advanced screen setting you refer to only affects the fonts and widgets ('close' buttons, scroll bars etc.) that Windows uses for desktop icons, application windows, the task bar and so on. If your display has lots of dots per inch then Windows will need to use larger fonts and widgets to avoid eye strain.

Personally I keep that setting at 96 dpi even when using hi-res small screens, as XP doesn't really handle the 120 dpi setting very well. It works but things like the taskbar look pretty ugly.

If you view an image that is 50 pixels wide then unless you zoom in it will still only take up 50 pixels of your display, no matter what dpi setting you choose in Display Properties.

Regards

Nelviticus

 

[oscarse]

Thanx for the reply. I guess I am still stuck on why a number of 120dpi is larger then 96dpi ... if all things are relative to the resolution PPI (pixels per inch) then we can probably assume the INCH in DPI is a misleading term (not actually an inch) ... Would this mean that lets say a font that is 1 inch in PPI takes 130 PPI to display at 96DPI will now be 125% larger if we select 120DPI because the DPI to PPI ratio of the screen doesn't change? In other words 130/96 = 162.5/120 therefore making the font larger? If this is the case then I think MS should remove the DPI context from this feature and just leave the % larger or smaller as I am certain I am not the only one perplexed with this setting.

 

[Nelviticus]

It's not as complicated as that. Allow me to explain.

At home I have a laptop with a 15.4" screen with a resolution of 1680 x 1050. I also have a desktop PC which has a 22" monitor, also with a resolution of 1680 x 1050. The laptop's screen is about 13.1" wide and 8.2" high; the desktop PC's screen is about 18.7" wide and 11.7" high. That means the laptop has about 128 dots per inch and the desktop 90.

If I use a 10pt Arial font on my big monitor it will be nice & readable; if I use the same font on my laptop it will be tiny and hard to read. Therefore, I need to use a bigger font.

The key point is that the display setting doesn't mean "choose a font that's 120 dpi" it means "choose a font suitable for a 120 dpi display". A higher dpi number means more stuff is packed into each inch so you need to make the stuff bigger in order to see it clearly.

Hope that makes it clearer!

Nelviticus