Mouse sensors, explained from scratch

How an optical sensor actually works

A modern gaming sensor is a tiny camera (an image sensor plus a low-power IR or red LED) pointed at the mousepad. It captures a low-resolution image of the surface texture many thousand times per second. A dedicated chip — the sensor's DSP — compares frame N to frame N-1 and outputs a (dx, dy) movement vector to the mouse's microcontroller, which then sends those movements to your PC over USB.

Everything else — DPI scaling, smoothing, angle snapping, lift-off detection — is logic the DSP runs on top of those raw frames. A 'great sensor' is one whose DSP outputs an honest (dx, dy) under as wide a range of speeds, surfaces, and lighting as possible, with no extra processing layered on.

DPI / CPI — what it really is

DPI (dots per inch) and CPI (counts per inch) mean the same thing in this context: how many movement counts the sensor reports for every inch the mouse physically travels. A mouse set to 1600 DPI moved one inch reports 1600 counts to Windows.

DPI is a sensitivity setting, not a quality setting. A 26,000 DPI sensor isn't 'better tracking' than an 800 DPI one — it can just translate motion at finer increments. Most competitive FPS players sit between 400 and 1600 DPI, and the most common pairing in pro-level Valorant, CS, and Apex is 800 DPI with a low in-game sensitivity. Higher DPI is useful for high-resolution monitors (4K desktops) and for productivity apps where you want to cover the screen quickly.

eDPI: the number that actually matters in games

eDPI = mouse DPI × in-game sensitivity. It's the effective sensitivity, and it's the only fair way to compare yourself to other players, because two people running 800 DPI / 0.5 sens and 400 DPI / 1.0 sens have identical aim despite different settings.

A more useful metric for ports between games is cm/360 — how many centimeters of mouse travel you need to do a full 360° turn. Aim-calculator sites convert your settings between any two games using cm/360 as the bridge.

Polling rate — how often the mouse talks to your PC

Polling rate, measured in Hz, is how many times per second the mouse sends an update to your computer. 1000 Hz means an update every 1 ms. Higher rates send smaller, fresher movement packets, which reduces the average input lag between physical motion and on-screen response.

IPS — the speed ceiling

IPS (inches per second) is the maximum speed at which the sensor can still track accurately. If you swipe faster than the sensor's IPS rating, it loses the surface and stops reporting motion until you slow down — your crosshair stops mid-flick.

Modern flagship sensors are rated for 650–750 IPS, which is far faster than any human can move a mouse on a normal pad. The figure mostly matters for very low sensitivities (high cm/360) where wild arm flicks are routine, and on slick glass pads where flicks travel further per gram of effort.

Acceleration tolerance — the G rating

The G (or g) rating is the maximum acceleration the sensor can keep up with — how quickly you can change speed without the sensor losing the surface. 50 G is the modern baseline. Like IPS, it's almost never a real-world limit; it's mostly a spec-sheet bragging right.

Lift-off distance (LoD)

LoD is how high you can lift the mouse off the pad before the sensor stops registering motion. Low LoD is generally desirable: low-sensitivity players reposition the mouse by lifting and replacing it, and a high LoD means the sensor keeps reading garbage motion during the lift.

• Most flagship mice let you choose between ~1 mm and ~2 mm LoD in software.
• On thick pads or with stick-on grip tape, real LoD can shift a fraction of a millimeter — recalibrate in software after surface changes.
• Some sensors offer surface calibration (Logitech, Razer, Pulsar) that fingerprints your pad to tighten LoD further.

Things you do not want the sensor doing

Smoothing

Software averaging that hides micro-jitter at the cost of feel. It adds latency and disconnects your hand from the cursor. Modern flagships have no smoothing in their native DPI range; budget mice sometimes engage it above a certain DPI.

Prediction (angle snapping)

The sensor 'helps' you draw a straight line by suppressing small deviations. Useful for drawing, fatal for aim. Turn it off — most gaming mice ship with it off by default.

Acceleration

Cursor speed scales with how fast you move, so the same physical movement covers different distances at different speeds. Destroys muscle memory. Make sure both Windows Enhance Pointer Precision and any in-mouse acceleration are off.

Ripple correction

Cousin of smoothing. Removes high-frequency wobble at the cost of a small latency penalty. Off by default on modern flagships.

Sensor families you'll see on spec sheets

PixArt (PAW / PMW)

PixArt makes the sensors used by most of the market. Their naming has been evolving — PMW3360 was the breakout in 2016; PMW3389 was the universal flagship for years; PMW3370/3395 raised tracking specs further; and the PAW3950 introduced motion sync and lower power draw. Endgame Gear, Pulsar, Glorious, VAXEE, Lamzu, and dozens of others use PixArt sensors, often with custom firmware tuning.

Logitech HERO

Logitech's in-house sensor line. HERO 25K (2019) and HERO 2 (2023, in the G PRO X SUPERLIGHT 2 and G502 X PLUS) emphasize low power draw — that's how the Superlight 2 hits ~95 hours of battery. Tracking quality is on par with PixArt flagships.

Razer Focus / Focus Pro

Razer's branded sensors are typically PixArt silicon with Razer firmware. Focus+ debuted on the Viper Ultimate; Focus Pro 30K (in the Viper V3 Pro and DeathAdder V3 Pro) adds asymmetric cut-off, smart tracking on glass, and motion sync to align sensor frames with USB polls.

Motion sync — small spec, surprisingly real

Motion sync (Razer's term; PixArt MotionSync, Logitech Hi-Res Scrolling is unrelated) synchronizes when the sensor reads movement with when the mouse sends a USB poll. Without it, you can get a slightly stale frame on each poll because the sensor read at a random offset; with it, the poll always carries the freshest sample. The result is more consistent cursor behavior, especially noticeable at higher polling rates.

What actually matters when comparing sensors

1. No smoothing, no prediction, no acceleration across the DPI range you'll actually use.
2. Native (not interpolated) DPI steps in the range you want (400, 800, 1600).
3. Sufficient IPS for your sens — basically any modern flagship clears this.
4. Configurable lift-off distance, ideally with per-surface calibration.
5. Stable polling at your chosen rate — check independent reviews for poll-rate spikes or motion delay graphs (rtings.com and the r/MouseReview community publish these).

Specs you can safely ignore on the box

• DPI numbers above ~10,000 — even pro players rarely use more.
• IPS and G ratings, once you're past ~400 IPS / 40 G — no one moves that fast on a normal pad.
• 'Up to 100M clicks' switch ratings — relevant only as a rough quality signal, not a competitive metric.
• RGB count, software 'AI', and marketing buzz around 'esports tuning'.