Relationship between mouse DPI, screen resolution and screen size

07
2014-07
  • user1301428

    I don't have the equipment at hand to test this, so before melting my brain on this, this is the scenario.

    Suppose that you are playing a FPS with your mouse set at 1000 DPI and your in-game sensitivity at 5. How would your game experience change keeping the same DPI but changing one or both of the other two variables, screen resolution or screen size?

    Same DPI but lower/higher resolution: would you have to readjust the in-game sensitivity to keep feeling the same? If the sensitivity remains the same but you have less/more pixels to travel across, will you feel your mouse more/less sensitive?

    Same DPI, same resolution but different screen size: if you keep everything the same, but the screen is bigger/smaller, will your mouse feel more/less sensitive because by doing the same wrist movement your cursor will cover more/less screen space?

    • Answers
  • harrymc

    As far as my understanding goes, screen size is not important. It's rather the screen resolution that is important.

    In the simplest (non-existent) case, each dot on the mouse's pad corresponds to one pixel on the screen. So, for example, if your screen resolution was 1920x1200 and your mouse was capable of a maximum DPI of 600, you'd have to move your mouse two inches to get from the bottom of the screen to the top. If your mouse used a DPI of 1200, it would only take one inch to make the same movement on the screen.

    Therefore higher mouse DPI allows you to move faster on the screen with less mouse movement. Higher resolution displays may require higher sensitivity or higher mouse DPI to attain the same amount of on-screen movement, or one would need a ridiculously large mouse-pad.

    Sensitivity is software based. It gets your dpi and divides or multiplies it to get the final dots-to-pixels sensitivity. It is just a multiplier of the input sent by the mouse. For example, if you had the mouse on 3600 DPI and then set the sensitivity to 2.5/10, it would function the same as 900 DPI on 10/10 sensitivity.

    There are cases where mouse sensitivity in the supplied mouse driver is applied in addition to Windows mouse sensitivity, it all ending with an unpredictable mess.

    So, for your questions:

    Same DPI but lower resolution : Mouse will cover larger physical screen territory with the same hand-movement. It will be harder to click exactly on a specific small area on the screen.

    Same DPI but higher resolution : Mouse will cover smaller physical screen territory with the same hand-movement. Working with small screen objects is easier as the mouse is "slower".

    Same DPI, same resolution but different screen size : Getting from one side of the display to the other will take more mouse movement. But if the same windows are displayed in the same size, working inside such a window will be the same. For getting faster across a large screen, you could use mouse acceleration together with fast and large gestures. However, in gaming mouse acceleration can make you overshoot your target.

    Both higher and lesser mouse DPI have their advantages. I am, for example, currently using a mouse that has a DPI switch button, so I can change the DPI to suite my current task.


    • Related Question

    Dual monitors on Windows - How do I set a different DPI or text size on each monitor?
  • dlux

    My laptop is a 15" wide screen running at 1600x1050, and in addition to that I connect an external 19" LCD which runs at 1280x1024. The problem with this setup is that if I increase the text size to make the laptop screen readable, the text on the external LCD is huge. Normal text on the LCD results in tiny text on the laptop.

    What options do I have to get around this?


    • Related Answers
  • techie007

    DPI settings affect the entire desktop, regardless of number or arrangement of monitors. You cannot have two different DPI settings on two monitors.

    Update:

    This is untrue as of Windows 8.1, which adds many DPI scaling enhancements, including per-display DPI settings. Although some may not find the implementation offers enough control.

  • Peter Mortensen

    A bit of a hack is:

    If you are always using a certain application on one screen, you can set that application to ignore DPI settings. For example, I have Visual Studio on my big monitor set to ignore DPI (100%). Everything else on my retina laptop monitor is at 145%.

    The setting "Disable display scaling on high DPI settings" is under compatibility under the properties menu of the application exe.

  • Leftium

    I solved this issue by changing the "apparent DPI" (and thus text size) of the monitors. Placing the external 19" LCD further away will reduce the apparent size of the font.

    If you don't want to/can't place the displays like that, you can also use the Thinkpad screen at a lower resolution to increase the apparent font size. Calculate the DPI here and make sure they match.

  • Daniel

    You (should) be able to. In Linux you could do it like this:

    1. Create a X VNC Server with the size of two times the smaller screen. For example: you have two monitors, same size, but 1920 and 1600 pixels wide: you make a virtual server of two times the better one: 3840px wide (1080px height).

    2. Open two VNC clients against the server you just created. Put one in each screen. Full screen. Scale 1:1. Scroll the window on the right to show the rightmost part of the Vnc server. Since the pixels are different size, everything will look bigger in the screen of 1600px. Zoom out that one until sizes fits.

    This is obviously very simple and has grave drawbacks (no direct rendering, probably slow, etc). But if you could do the same with proper framebuffers and such...

  • Mathias Lykkegaard Lorenzen

    A new feature in the upcoming Windows 8.1 update for Windows 8 is to have the same scaling on several screens, despite their physical size. It's one of the features I've been waiting a long time for.

  • techie007

    As other answers have pointed out, DPI settings can't be adjusted per-monitor (or per-application).

    If you need specific applications running in a different DPI than the rest of the desktop, consider using a virtual machine.

  • t3mujin

    A workaround (although I haven't found how to do it in Windows 7) is enabling desktop panning/scrolling, that way it could be possible to set any resolution in smaller displays so font size would be similar.

  • Phantom Yoda

    You can change the DPI settings in Windows 7 at:

    Control Panel > Display or Control Panel > Display > Set custom text size (DPI)