Windows 10: Why is there a huge difference in DPI settings between 145% and 150%?

I've had a problem very occasionally with some programs that don't take into account that some people will select a different DPI setting and their text spills over so its not visible. Thankfully this is rare. But I just noticed when I changed from 150% to 145% there was a huge difference in the size of the window for the driver of a Logitech webcam. Is this typical? Its incredible that a company as big as Logitech makes these mistakes. There's not even much text in the window which makes it even more absurd. But now I'm noticing quite a difference in text size in other areas between 150

:)

 

Dual monitors with different DPI settings do not give correct scaling

An issue with DPI scaling arises when using two different scaling factors. The screen with the lower DPI display is fuzzy/blurred (most easily seen in text).

Hardware and settings

These are the hardware and settings involved:

• 1x primary 3840x2160 27" monitor with DPI scaling set to 150% (because regular text is unreadable at 27").
• 1x secondary 1920x1080 24" monitor with DPI scaling set to 100%, displaying blurry text and images at these settings.

Workarounds

When I use the same DPI scaling on both monitors the display shows correctly. This gives two undesirable workarounds:

• Setting 100% DPI scale on the UHD screen fixes display, but makes text unreadably small on this monitor.
• Setting 150% DPI scale on the HD screen fixes display, but makes text so large I barely have any screen space left on this monitor.

Is there per chance a better solution to this problem? Is this a Windows bug or am I using DPI scaling in the wrong way?

EDIT: Here's the system info from dxdiag just in case.

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System Information

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Time of this report: 11/14/2015, 13:09:59

Machine name: -

Operating System: Windows 10 Pro 64-bit (10.0, Build 10240) (10240.th1_st1.151104-1714)

Language: Dutch (Regional Setting: Dutch)

System Manufacturer: To Be Filled By O.E.M.

System Model: To Be Filled By O.E.M.

BIOS: BIOS Date: 07/09/14 21:30:44 Ver: 04.06.05

Processor: Intel(R) Core(TM) i7-4770K CPU @ 3.50GHz (8 CPUs), ~3.5GHz

Memory: 8192MB RAM

Available OS Memory: 8112MB RAM

Page File: 5936MB used, 3454MB available

Windows Dir: C:\WINDOWS

DirectX Version: 12

DX Setup Parameters: Not found

User DPI Setting: Using System DPI

System DPI Setting: 144 DPI (150 percent)

DWM DPI Scaling: Enabled

Miracast: Available, with HDCP

Microsoft Graphics Hybrid: Not Supported

DxDiag Version: 10.00.10240.16384 64bit Unicode

 

Dual monitors with different DPI settings do not give correct scaling

Hello Jayant and thank you for your reply.

As described in the threads you provided I updated my graphics drivers (though they were already on the latest version) and tried changing my screen resolution back and forth. Neither helped the situation sadly.

The solution that suggested editing the registry seems to be aimed at disabling DPI scaling for specific applications. However, this is not my aim as disabling DPI scaling would indeed remove blurring but text would stay unreadably small.

The Windows Dev Center article did confirm two things for me.

• There are DPI-unaware applications which will be scaled up by Windows making them appear blurry. This behaviour is correct as described in the Windows Dev Center article and as seen in the first image of the following article:
  
  http://www.anandtech.com/show/7939/scaling-windows-the-dpi-arms-race/3 These applications are not the problem I am describing, we cannot expect Windows to magically show DPI-unaware applications in high detail. An example of a DPI-unaware application is
  Sublime Text 2 and the older version of VLC as shown in the AnAndTech article.
  
• There are DPI-aware applications which experience blurring when there are two differing DPI scaling settings present. The application blurring occurs on the screen with the lower DPI scale. I do not know the behaviour when there are more than two screens
  with more than two differing DPI scales present. Examples of DPI-aware applications are Google Chrome and Visual Studio 2015.

A little experiment

Lets look at an example of bullet point 2 using screenshots of Google Chrome rendering a webpage. The screenshots were made using the Windows screenshot functionality and cropped in paint.net.

Image 1 - Correct DPI/scaling on HD screen

The first image is an example of proper DPI on the 1920x1080 (HD) screen. The 3840x2060 (UHD) is also connected, but DPI scaling is disabled (set to 100%) for both screens. In this scenario everything displays as expected, but let me remind you that this
is not a solution because at 100% DPI scale text on the 27" UHD screen is too small, as mentioned)



Image 2 - Incorrect DPI/scaling on HD screen

This second image taken from the same HD screen is clearly more blurry than the first image. In this scenario the DPI scaling for the UHD monitor has been set to 150% (and the user account has been logged out and in as recommended by Windows when changing
the setting). It appears that the scaling for the UHD monitor somehow affects the render on the HD screen, despite it having in fact the same settings as in the previous image. The blurring effect occurs in other applications like VS2015 and Windows Explorer
as well.



Image 3 - Correct DPI/scaling on UHD screen

The third and last screenshot is taken with the same settings as image 2, but from the UHD screen. As expected this image is larger because Windows requested from Google Chrome to render 150% pixels for the same area of the application to keep my eyes happy.
This and the first image assert that Chrome is a DPI-aware application which can indeed render sharp images at different DPI scales.



An interesting side note is that DPI-unaware applications do render at the prober 100% DPI scale without blurring when displayed on the HD screen with the settings used in image 2 and 3.

I hope this clears up what my concerns are because I can't get much more detailed than this.

 

DPI 150%+ Issue with some apps being very big.

Hello,

I am having trouble running Guitar Pro & MuseScore at 150%+ DPI, everything is big, with Guitar Pro at 100-125% everything is equally small (No Difference in 100% vs 125%)

I tried every combination of the DPI settings in the properties menu of Guitar Pro, it doesn't fix the issue.

See Screenshots

I am on Build 19041.329