Sensor and Performance

The iMouse X3 is equipped with the SPCP-6653B. I had to open the mouse to figure this part out. I haven't been able to find out which specifications this sensor has. The only thing I know is that it uses external illumination, is a 12 pin, and apparently doesn't need a dedicated MCU (SoC). Out of the box, no less than seven pre-defined CPI steps are available: 500, 1000, 1600, 2400, 3200, 4800, and 6400 CPI. I'm not sure where Adesso got the "500" value from as the first CPI step is set to 600 by default.

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 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.


I've restricted my testing to the four most common CPI steps, which are 400, 800, 1600, and 3200 CPI. As you can see, the deviation is really bad, but at least it's consistently bad.

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.



Typically, this test would be used to determine whether there is any smoothing present by looking at any possible "kinks" showing up. Since the PCS of this sensor is incredibly low, however, I can't even accelerate it to where a framerate transition would be plainly visible. Let's take a look at the tracking quality then. We can see that SPI timing has ridiculous amounts of jitter. Notice how the response becomes increasingly worse the higher the speed—in each plot, the grouping is very tight at the start only to go completely haywire after passing a certain speed threshold (roughly 0.5 m/s), moving back to that initial tight grouping only after again dropping below that speed threshold. Overall tracking quality is very poor, no matter the CPI step.

Usually, I'd try to verify the results from the xCount plots here by plotting the xSum against the G403. However, not only did xCount testing prove inconclusive, xSum testing results varied wildly as well. Compared to the G403, I have gotten results anywhere between 0–4 ms motion delay, with no clear pattern anywhere to be seen. If we take the results from the Paint test below into account, it is reasonable to assume that the smoothing level is low to none, though. All in all, I'm not confident in making any claims here, but I can say that this degree of variance and inconsistency isn't exactly ideal in and of itself.

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. PCS is exactly 1.75 m/s. The first plot shows a 2 m/s swipe to make the PCS graphic. When going faster, significant malfunctions can be produced, which result in highly erratic behavior, as seen in the second plot. When forcing this kind of malfunction on the desktop, the cursor indeed travels backwards. Exceeding the PCS in-game results in a so-called spin-out, where the cursor shoots to the ground.

Polling Rate Stability

All four possible settings (125 Hz, 250 Hz, 500 Hz, and 1000 Hz) show higher than average variance. Additionally, 1000Hz exhibits weird patterns, as seen here:

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. There is no jitter visible at 400, 800, and 1600 CPI, but significant jitter can be observed at 6400 CPI. Furthermore, no sensor lens rattle is present.

Lift-off Distance

The iMouse X3 does not support adjusting LOD. At the only available (default) setting, the sensor still tracks at a height of 2 DVDs, but not at a height of 3 DVDs. It should be kept in mind, however, 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 G203. Click latency has been measured to be roughly +16 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.