Sensor and Performance

The Zowie S2 comes with the PMW3360, which is one of PixArt's best optical sensors as of now. According to its specifications, the 3360 is capable of up to 12,000 CPI as well as a maximum tracking speed of 250 IPS, which equals 6.35 m/s. Zowie restricts the sensor to four pre-defined steps, however, which are 400, 800, 1600, and 3200 CPI.

CPI Accuracy

"CPI" (short for counts per inch) describes the amount of counts registered by the mouse if it is moved exactly one inch. There are several factors (firmware, mounting height of the sensor not meeting specifications, mouse feet thickness, mousing surface, among others) which may contribute to nominal CPI not matching actual CPI. It is impossible to achieve a perfect match, but ideally, nominal and actual CPI should differ as little as possible. In this test, I'm determining whether this is the case or not. However, please keep in mind that said variance will still vary from unit to unit, so your mileage may vary.


As you can see, deviation is very low, which is an excellent result. For the longest time, older Zowie mice were typically below specifications, but that is not the case here.

Motion Delay

"Motion delay" encompasses all kinds of sensor lag. Any further sources of input delay will not be recorded in this test. The main thing I'll be looking for in this test is sensor smoothing, which is an averaging of motion data across several capture frames in order to reduce jitter at higher CPI values, which increases motion delay. The goal here is to have as little smoothing as possible. As there is no way to accurately measure motion delay absolutely, it can only be done by comparison with a control subject that has been determined to have the lowest possible motion delay. In this case, the control subject is a G403, whose 3366 sensor has no visible smoothing across the entire CPI range.


First I'm looking at an xCounts plot to quickly gauge whether there is any smoothing, which any visible "kinks" would indicate. Whereas the 1600 CPI plot does not show any kinks, the 3200 CPI plot does. This is to be expected as the 3360 has 32 frames of smoothing at and above 2100 CPI, which amounts to an added motion delay of roughly 4 ms at the lowest possible speed.


Second I'm looking at the xSum plots of the four available CPI steps, which are 400, 800, 1600, and 3200 CPI. The line further to the left denotes the sensor with less motion delay. As you can see, motion delay is identical at any step but 3200 CPI, where the differential is roughly 4 ms, which merely confirms the results above.

Speed-Related Accuracy Variance (SRAV)

What people typically mean when talking about "acceleration" is speed-related accuracy variance (or SRAV for short). It's not about the mouse having a set amount of inherent positive or negative acceleration but about the cursor not traveling the same distance if the mouse is moved the same physical distance at different speeds. The easiest way to test this is by comparing it to a control subject that is known to have very low SRAV, which in this case is the G403. As you can see from the plot, no displacement between the two cursor paths can be observed, which confirms that SRAV is very low.

Perfect Control Speed

Perfect Control Speed (or PCS for short) is the maximum speed up to which the mouse and its sensor can be moved without the sensor malfunctioning in any way. I've only managed to hit a measly 4 m/s (which is within the proclaimed PCS range), at which speed no signs of the sensor malfunctioning can be observed.

Polling Rate Stability

All three possible settings (125 Hz, 500Hz, and 1000Hz) look nice and stable.

Paint Test

This test is used to show any potential issues with angle snapping (non-native straightening of linear motion) and jitter, along with any sensor lens rattle. As you can see, no such issues can be observed. Furthermore, there is no sensor lens rattle.

Lift-off Distance

As far as I can tell, the S series does not support adjusting LOD. The only available (default) setting is very low, as it doesn't track at a height of 1 DVD. However, keep in mind that LOD may vary slightly depending on the mousing surface (pad).

Click Latency

Since mechanical switches are being used for the buttons in most mice, debouncing is required in order to avoid unintended double clicks. Debouncing typically adds a delay, which shall be referred to as click latency. As there is no way to measure said delay directly, it has to be done by comparing it to a control subject, which in this case is the Logitech G100s. Click latency has been measured to be roughly +6.5 ms when compared to the SteelSeries Ikari, which is considered as the baseline with 0 ms. Please keep in mind that the measured value is not the absolute click latency. Comparison data comes from this thread as well as my own testing, using qsxcv's program.