Some Things Count
Without trying to bore you to technical tears, inside an optical mouse are a camera and an image sensor and a red light (red is better for details) so the camera can see. There’s also a digital signal processor (DSP). As the mouse moves across the terrain (or as you roll the trackball with your thumb), the camera is clicking away, sending images to the sensor, which is passing them on to the DSP. The number of changes in the terrain, left/right and up/down are counted and the movement of the mouse is extrapolated to correspond to your cursor movement on the screen. Software (the mouse driver, if required) is used to fine tune the results or modify them, as you prefer.
So, if you move the mouse and the pointer moves on the screen a certain number of pixels or dots, why am I getting all semantic over not using DPI to describe the mouse’s resolution? Because, officially, it’s the number of changes counted –or, simply, the number of counts—that tells the mouse how far the cursor should move. Those in the know use “counts per inch” (CPI) and now you know.
Robust Rodentia
Typically, mice run in the range of about 100 to 400 CPI. That assortment, small as it is, worked great when our screen resolutions were 640x480 or even 800x600. There was no real need for speed in getting from here to there or back again. Then our screen resolutions began to expand as display technology improved. Today, 1280x1024 is really not that uncommon. Honestly, a 400CPI mouse would work fine at that size if it weren’t for that horrific despoiler of children and others of finer computing sensibilities: gaming!
Gaming has sparked much of the evolution of computing for about the last ten years. It’s because of the demands made by games that our PCs have become what they are. The most popular games are the action variety, particularly the first person shooter (FPS) genre. During the course of such games, you’ll need to move from here to there quickly to avoid being blown away by another player or to precipitate the demise of your opponent. Thanks to larger screen resolutions, getting to that terminus point needs to be done quickly. Thus was born the 1200, 1600, and even 2000 CPI mouse. Start here and, zip, you’re over there almost without moving the optical rodent.
Exceptions Added to the Rule
Before the rest of the computing world takes virtual Crayola to paper bag and sends me hate mail, let’s amplify the situation. Along with gamers, graphic artists, and even lowly consumers attempting to diddle with results of digital cameras, also have a need to move quickly on the screen rather than annoyingly skate a mouse along their desks several times, across a small space, wedged between keyboard and wall.
Here’s the other shoe, however: Mice with big CPI values will get you there quickly, but what happens once you arrive? FPS gamers need to aim at their target. Graphic artists and diddling consumers need to then work with small areas. Even if you’re only moving from spreadsheet cell A1 to ZZ2768, when you’ve arrived at your chosen location you then need to be able to address the contents of a relatively small space – a single cell, or even a single pixel. Those are agonizingly small objects at 1280x1024 when your mega mouse is still thinking big.
The solution, which is neither simple nor single-minded, will occur to you next time.
Bill O'Brien can be blamed for more than 2,000 articles on computers and technology topics. With his writing partner, Alice Hill, Bill co-authored "The Hard Edge," the longest-running (1992 to 2004) technology column penned by a techno duo. For more, go to www.technudge.com.