Evaluating Mice: DPI And Polling Rate
Dots Per Inch (DPI)
The single most common and direct measurement for comparing the sensitivity of a mouse is dots per inch (DPI). This term essentially refers to the speed that a user can manipulate the on-screen cursor. For example, if you pair a 2,000 DPI mouse to a screen with a resolution of 2,000 horizontal pixels, you would only need to move the sensor one inch to completely cross the width of the display.
However, sensitivity levels are typically configurable, which you've likely seen from fiddling around in a driver's corresponding control app or a game's settings. In both cases, the computer either interpolates or extrapolates cursor movement based on the information being fed to it by the mouse. This is a kind of software scaling, and it doesn’t really increase the ability of a mouse to process and transmit more information about its movement faster.
Modern mice employ tiny cameras that take hundreds of pictures per second while shining a bright light (typically red) on the surface. By analyzing these pictures, a controller in the mouse can figure out where it’s going relative to its former position. It then breaks that information down and sends it to the computer. The DPI setting given by the manufacturer is the maximum pixel/inch ratio that the mouse can reliably operate at.
However, as many have pointed out in the past, using a super-sensitive mouse won’t necessarily help your game.
So, mouse DPI is also tied to the size of your monitor, in a sense. Crossing 2,000 pixels with a 2,000 DPI mouse only requires one inch of movement, but crossing 4,000 pixels requires you to move that same mouse two inches. The main reason DPI settings still matter has a lot more to do with the fact that monitor resolutions, especially those on gaming rigs with multiple screens, continue to grow.
Moreover, most gaming mice have one or two dedicated buttons for on-the-fly DPI adjustments, allowing you to tailor sensitivity as needed. In first-person shooters, for example, it’s not always helpful to have sensitivity cranked up to 11. When it comes to sniping through a zoomed-in scope, a slight twitch can really throw you off-target. Lower DPI is often better for those situations.
Instead of dealing with constant adjustment, many folks prefer one low- to mid-speed setting during game time. It's not uncommon for them to move their mouse quickly, pick it up, and put it back down again to get a full rotation. This where polling rate, another critical mouse stat, comes into play.
Polling rate is simply the interval at which a mouse reports its position to the computer. A 125 Hz rate means information is being communicated to the host 125 times every second. Accurate reporting depends on the number of data points a mouse can produce and send to the computer. Players who prefer lower sensitivity settings may want to set their polling rate as high as possible in order to reduce the likelihood of their movements being misinterpreted. Conversely, if you prefer higher sensitivity settings, you may want to reduce polling rates to avoid random, natural twitches from interfering with on-screen accuracy.
Creating objective tests, and understanding which would actually translate into a substantive difference in terms of game performance, is a bit challenging. All of these mice use the current generation of image sensors, giving them all roughly the same DPI, they all connect with USB 2.0, and they generally include similar features. Keeping all of that in mind, we thought it would be best to instead check for failures. But what could we do, within reason, that would cause a mouse to under-perform?
To start, we used an array of utilities able to track mouse output to the computer, including polling rate data and positions on the X and Y axes. With this data, we should have been able to determine each mouse's ability to report its position without error. That was the plan, at least. In reality, we weren't able to trigger a failure on any of these models.