Sensor and Performance

The Ninjutso Katana 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, four pre-defined CPI steps are available: 400, 800, 1600, and 3200.

Sensor "Skipping"?

When skimming through user reports of the Katana, one inevitably will find talk about sensor or cursor "skipping." The issue with this issue is the difficulty of properly verbalizing what is happening. Essentially, during any sort of motion, the sensor will suddenly "jump"; that is, the cursor will go from a given position to a different one in a single motion without any user input. In my case, these jumps were restricted to the negative y-axis. Luckily, I have been able to catch such a jump in Paint—notice that the vertical line does not correlate to a user input. From what I can tell, this malfunction usually happens every 20–40 minutes and entirely at random, which is why reproducing it is nigh impossible. Furthermore, it is unclear whether all or just some copies are affected. Calling this behavior "jarring" would be an understatement, and I consider it a major flaw.

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 nominal CPI not matching actual 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 differ from unit to unit, so your mileage may vary.


I've restricted my testing to the four most common CPI steps, which are 400, 800, 1600, and 3200. As you can see, deviation is minimal, which is an excellent 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. Note that the G403 is moved first and thus receives a slight head start.


First, I'm looking at two xCounts plots—generated at 1600 and 16,000 CPI—to quickly gauge whether there is any smoothing, which would be indicated by any visible "kinks." While just barely visible, such a kink is present in the second plot, strongly suggesting there being smoothing. As an aside, SPI timing jitter is appreciably low.


In order to determine motion delay, I'm looking at xSum plots generated at 1600, 3200, and 16,000 CPI. The line further to the left denotes the sensor with less motion delay. There is no motion delay differential at 1600 CPI. At and above 1900 CPI, where the 3389 has 32 frames of smoothing, a motion delay differential of roughly 4 ms can be observed. Smoothing is doubled at 6000 and 11,300 CPI each, resulting in a motion delay differential of 15 ms at 16,000 CPI.

Speed-related Accuracy Variance (SRAV)

What people typically mean when they talk 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 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 5 m/s, which is within the proclaimed PCS range and shows no sign of the sensor malfunctioning.

Polling Rate Stability

All of the available polling rates (125, 250, 500, and 1000 Hz) exhibit periodic outliers.

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 1600 and 3200 CPI, the latter of which already has smoothing applied. The same goes for 16,000 CPI, which shows moderate jitter. Lastly, there is minor sensor lens movement.

Lift-off Distance

The Katana offers two pre-defined LOD levels. At the "Low" setting, the sensor does not track at a height of 1 DVD (<1.2 mm). Using the "High" setting, the sensor does track at a height of 1 DVD (1.2 mm<x<2.4 mm, with x being LOD height), but only sporadically at a height of 2 DVDs. Keep in mind that LOD may vary slightly depending on the mousing surface (pad) it is being used on.

Click Latency

In most computer mice, mechanical switches are being used for the main buttons, which require debouncing 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 outside of using a USB analyzer, it has to be done by comparing it to a control subject, which in this case is the ASUS ROG Chakram Core. The test setup involves wiring the NO pin of one of the main button switches of the test subject to one of the control subject, and qsxcv's program is used to measure the relative delay between them. Doing so is only possible if the devices in question are plugged into the PC through a wired connection. The Zaunkoenig M2K has been posited as the baseline for being within 0.1 ms of the possible minimum click latency of a high-speed device and within 0.2 ms of a hypothetical absolute minimum. As such, the resulting values may be considered quasi-absolute.

By default, the debounce time slider within the software has no effect. Ninjutso has provided me a beta firmware which enables this functionality. Using the 1 ms setting, click latency has been measured to be roughly +2.3 ms, with standard deviation being 0.57 ms. Using the default 10 ms setting, click latency has been measured to be roughly +11.1 ms, with standard deviation being 2.46 ms.