Microsoft has officially revealed that Windows 8.1 brings improvements to deal with high-DPI scaling issues on high-resolution displays, such as in 4K monitors, high-DPI tablets, notebooks, multi-monitor setups, and to help developers to optimize Windows 8 apps to scale automatically based on the screen DPI (dots per inch).
New DPI setting for high-resolution displays
Although, high-res displays can offer an amazing viewing experience, it also brings new sets of problems, because when resolution increases, it means that pixels get smaller, as such elements on the screen will appear smaller too, and this makes readability and navigation a big issue. To address these problems in Windows 8.1 the DPI scaling options has increased from “Larger –150%” to “Extra large — 200%”, which Microsoft assures will provide clear and crisp images, graphics, and text (of course you can always use a custom sizing option).
Multi-monitor DPI scaling in Windows 8.1
Microsoft is also addressing scaling issues in multi-monitor setups. Before in Windows 8, users had to compromise by configuring one DPI scaling size for all monitors. Now in Windows 8.1 supports per-display DPI scaling, and by default settings are based on the new “overall scaling” option in the control panel. — This is a huge deal and even more for Surface users who were one of the most affected by this scaling issue.
Windows 8.1 apps new DPI scaling
Finally the software maker is fixing the scaling issue with apps. At first glance this may not look like a problem, but if you’re using a 4K-res monitor and the DPI is set to 200%, the app’s elements (buttons and other options) will look fine. However if you are using a photo app, the image will also scale, which means that you won’t see the natural resolution of that image and this isn’t the ideal experience.
The fix to this problem comes in form of API that developers can use to know how to scale a photo correctly to 100%, while scaling the DPI of the elements on app to a higher value.
Source Extreme Windows Blog