Mouse myth: When a mouse performs differently at different speeds, that’s a problem called “acceleration.”
Verdict: False. This is a real issue, but acceleration is an inaccurate term to describe it. Logitech’s mouse experts offer two alternatives: “resolution error versus speed” and “speed-related accuracy variance.”
Acceleration is a big, complicated issue. Here’s how it’s usually described on the Internet: if you swipe your mouse quickly across the mousepad, and then slowly move it back to where it started, your cursor should return to its exact starting position. If it doesn’t, the mouse is exhibiting some form of acceleration, meaning it’s translating your physical movements differently at different speeds. And that’s bad, right? Because you want an exact 1:1 ratio between your movements and the cursor. Otherwise, in an intense FPS firefight, for example, you could quickly swing your mouse around and misjudge the distance the cursor’s going to move.
So what causes this problem? And why is “acceleration” actually a bad term for it?
Pate: “Acceleration as it’s understood by people on the internet, particularly as it’s applied to a certain family of laser-illuminated sensors, is actually an issue with accuracy relative to the speed that the mouse is being moved. It’s not that the mouse has an inherent amount of acceleration in a positive or negative direction. What it has is a difficulty to make the cursor travel the same distance if you move the mouse the same physical distance at different speeds. It’s real difficult to kind of parse everything that I just said, and it’s real easy to say ‘laser has acceleration.’”
François Morier calls acceleration “resolution error versus speed,” but it’s important to note that in this context, “resolution” has nothing to do with image quality (don’t be thinking 1080p vs. 4K, etc).
Morier: “Resolution to me, means the translation between your hand movement and the distance you cover on the screen. It’s just a factor of relation between, I move one inch, how many pixels I’ve covered on the screen. This is the resolution.”
It’s not that the mouse cursor or sensor is accelerating when you move the mouse different speeds. The problem is there’s a discrepancy between the data the mouse is reading at those different speeds. Describing why that happens is pretty complicated, and we’ll delve into the really technical stuff in the next myth, about DPI. But on the high level, resolution error versus speed happens due to mouse sensors picking up too much noise in their image as they scan the mousing surface. As you may remember from the last myth, this is more common in laser-illuminated mice.
As Morier explains, when you move a mouse, there’s only one “right” direction for the sensor to read: the exact direction you’re moving. When the sensor picks up noise, that’s adding “counts” of movements in the wrong directions—little tiny movements upwards or downwards as you move the mouse sideways, for example. Adding those incorrect counts is “changing the number of count you'll have at the end [of a mouse movement]. So if you travel full horizontal but your system is doing something like that, you will lose a part of the horizontal motion, because part of the horizontal motion will be reported vertically, so at the end, your trajectory will be shorter.”