Sensor and Performance

The Zephyr Gaming Mouse is equipped with the PixArt PMW3389. According to specifications, the 3389 is capable of up to 16,000 CPI, as well as a maximum tracking speed of 400 IPS, which equals 10.16 m/s. Out of the box, five pre-defined CPI steps are available: 800, 1600, 3200, 6400, and 16,000 CPI. Retail units will also include a 400 CPI step.

CPI Accuracy

"CPI" (short for counts per inch) describes the number of counts registered by the mouse if it is moved exactly an 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 actual CPI not matching nominal CPI. It is impossible to always 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 well.


As mentioned above, my prototype lacks the 400 CPI step, so testing 800, 1600, and 3200 CPI will have to do. As you can see, deviation is quite small and consistent, which is important as the Zephyr Gaming Mouse lacks software for fine-tuning the CPI. Overall, a very good result.

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 describes an averaging of motion data across several capture frames in order to reduce jitter at higher CPI values, increasing motion delay along with it. 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 has no visible smoothing across the entire CPI range.


First, I'm looking at two xCounts plots—generated at 1600 and 3200 CPI—to quickly gauge whether there is any smoothing, which would be indicated by any visible "kinks." As you can see, no such kinks can be observed at 1600 CPI, whereas at 3200 CPI, it's plainly visible. This is in line with what to expect from a 3389. We can also see that SPI timing jitter levels are quite low. Additionally, there are a couple of visible outliers, which likely are polling outliers—see below for more details.


Let us take a look at three additional xSum plots, generated at 1600, 3200, and 16,000 CPI. The line further to the left denotes the sensor with less motion delay. At 1600 CPI, motion delay is identical. 3200 CPI shows a motion delay differential of roughly 3 ms, while 16,000 CPI shows a whopping 18 ms. This is in line with expectations as the PMW3389 has 32 frames of smoothing at and above 1900 CPI, which is then doubled at 6000 CPI and 11300 CPI. I've also found a very peculiar oddity I wasn't able to reproduce consistently. Occasionally, motion delay increases for no apparent reason mid-swipe:

Speed-Related Accuracy Variance (SRAV)

What people typically mean when they talk about "acceleration" is speed-related accuracy variance (or short SRAV). 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 comparison with 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 4.0 m/s (which is within the proclaimed PCS range), at which no sign of the sensor malfunctioning can be observed. However, the outliers seen earlier make an appearance here as well.

Polling Rate Stability

The Zephyr Gaming Mouse supports but a single polling rate: 1000 Hz. As you can see, polling rate drops to 500 Hz quite frequently. These are the outliers seen in the xCount plots above. It's also a possible cause of the motion delay oddities shown earlier.

Paint Test

This test is used to indicate 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 issues with angle snapping can be observed. No jitter is visible at 800, 1600, and 3200 CPI, the latter of which already has smoothing applied, which takes care of the jitter. 6400 CPI already shows some jitter despite the second stage of smoothing which is already active here. At 16,000 CPI, jitter is very high. Lastly, minor sensor lens rattle can be observed.

Lift-off Distance

The Zephyr Gaming Mouse does not support adjusting LOD. This is unfortunate as the 3389 would be fully capable of this. At the only available (default) setting, LOD is low, as the sensor does track at a height of 1 DVD, but not at a height of 2 DVDs (1.2 mm<x<2.4 mm). Keep in mind that LOD may vary slightly depending on the mousing surface (pad) it is being used on.

Click Latency

Since mechanical switches are being used for the buttons in most computer mice, debouncing is required in order to avoid unintended double clicks. Debouncing typically adds a delay (along with any potential processing 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 +6.7 ms 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.