Sensor and Performance

The G604 is equipped with the HERO 16K. According to specifications, the HERO 16K 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.

CPI Accuracy

"CPI" (short for counts per inch) describes the number 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. As you can see, the deviation isn't too large, but not entirely consistent either, which is a decent result. In order to account for the measured deviation, I've set steps of 400, 800, 1550, and 3100 for my testing.

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.

As the G604 is incapable of operating wired, measuring the isolated wireless delay is impossible. Consequently, the subsequent tests include any kind of delay without any further differentiation between sensor or wireless delay. All testing was done using the regular 2.4 GHz "LIGHTSPEED" wireless mode. Due to the lack of a Bluetooth-enabled device I'm unable to test the Bluetooth mode. That having been said, the lowered polling rate as well as the properties of the transfer protocol make Bluetooth mode unsuitable for anything that isn't office usage anyway.


The HERO 16K doesn't have fixed framerate levels, which has no framerate transitions show up in these two xCount graphs. While the 1600 CPI plot shows clean tracking with little jitter, the 16,000 CPI plot doesn't look quite as nice.


Here, I'm looking at xSum plots generated at 1600, 9000, and 16,000 CPI. The line further to the left denotes the sensor with less motion delay. At all three tested steps, motion delay is consistently sitting at 1–1.5 ms. Due to this consistency I'm inclined to believe that there is no smoothing across the entire CPI range, and that the measured delay is identical with the wireless delay.

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 m/s (which is within the proclaimed PCS range), at which speed no sign of the sensor malfunctioning can be observed.

Polling Rate Stability

For wired mice, polling rate stability merely concerns the wired connection between the mouse (SPI communication) and the USB. For wireless mice, another device that needs to be kept in sync between the first two is added to the mix: the wireless dongle/wireless receiver. I'm unable to measure all stages of the entire end-to-end signal chain individually, so testing polling rate stability at the endpoint (the USB) has to suffice here.


First, I'm testing whether SPI, wireless, and USB communication are synchronized. Any of these not being in sync would be indicated by at least one 2 ms report being visible, which would be the result of any desynchronization drift accumulated over time. As you can see, several 2 ms reports are visible, which confirms that the polling of the entire signal chain is not in sync.


Second, I'm testing general polling-rate stability of the individual polling rates in wireless mode. Running the G604 at a lower polling rate can have the benefit of extending battery life. While 125 Hz and 250 Hz show near-perfect results, both 500 Hz and 1000 Hz don't look quite as clean. Still, overall polling stability is sufficiently high for a wireless device.

Paint Test

This test is used to reveal any potential issues with angle snapping (non-native straightening of linear motion) and jitter, along with any sensor lens rattle. I'm testing 400, 1600, 9000, and 16,000 CPI. No issues with angle snapping can be observed at any CPI step. At 400 and 1600 CPI, no jitter is visible. At 9000 CPI, jitter is already excessive, and reaches comical levels at 16,000 CPI. This is in line with what to expect from a smoothing-free sensor. I consider the level of jitter at the latter two levels unusably high. Lastly, there is no sensor lens rattle.

Lift-off Distance

The G604 does not support manually adjusting the LOD. At the only available (default) setting, the sensor does not track at a height of 1 DVD. Keep in mind that LOD may vary slightly depending on the mousing surface (pad) it is being used on.

Click Latency

For some reason I'm unable to get any readings using my usual test setup. I've verified the setup several times, but no dice. That said, I did some testing using a different method, which gives me reason to believe that click latency on the G604 is largely the same as on every other recent Logitech mouse; i.e., around +4–5 ms compared to the SteelSeries Ikari (which acts as the baseline).

One thing I've noticed is that the main-button switches run at a very low voltage. While I don't know the exact specifications (operating voltage) of the switches in question, running switches at too low a voltage can lead to accelerated degradation, which can in turn result in unintended double clicks.