Sensor and Performance

The Corsair M75 Air is equipped with the Marksman sensor, whose designation is PixArt PAW3393-T4QU, and which I believe to be based on the PAW3399. According to specifications, the Marksman is capable of up to 26,000 CPI, as well as a maximum tracking speed of 650 IPS, which equals 16.51 m/s. Out of the box, a single pre-defined CPI step is set, which is 1200. This also represents the maximum number of steps.

All testing was done on the latest firmware (5.6.20/5.4.17). As such, results obtained on earlier firmware versions may differ from those presented hereafter.

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, there is no deviation at all, which is a perfect result.

2000 Hz USB Polling: Does it work?

Corsair promises a USB polling rate of 2000 Hz on the M75 Air, both in wired and 2.4 GHz mode. Now, the question is: Does it work? The short answer is no. First of all, the M75 Air is detected as a USB full-speed device, which already calls the ability to deliver actual 2000 Hz polling into question. Looking at an interval plot then removes any remaining doubt:


As you can see, the mouse simply sends two identical updates in every packet, both in wired and 2.4 GHz mode. Doing so serves no purpose other than faking readings. In actuality, no additional data is submitted, thus rendering the 2000 Hz polling functionally equivalent to 1000 Hz polling. In 2.4 GHz wireless operation (second plot), the M75 Air fails to do even that, and instead does non-duplicated 1000 Hz for the majority of time. For comparison, this is how things are looking on Corsair's own M65 RGB Ultra, a USB high-speed device capable of true 2000 Hz polling:


The difference is palpable to where no further discussion is necessary. Accordingly, I'll stick with 1000 Hz for the remainder of 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 Logitech G403, whose PixArt PMW3366 sensor has no visible smoothing across the entire CPI range. Note that the G403 is moved first and thus receives a slight head start.

Testing is restricted to 2.4 GHz mode as Bluetooth is not suitable for non-casual gaming applications.

Wired Testing

First, I'm looking at two xCounts plots—generated at 1600 and 26,000 CPI—to quickly gauge whether there is any smoothing, which would be indicated by any visible "kinks." As you can see, neither plot shows any, which strongly suggests there not being any smoothing. Despite the sensor supporting it in hardware, MotionSync is disabled.


In order to determine motion delay, I'm looking at xSum plots generated at 1600 and 26,000 CPI. The line further to the left denotes the sensor with less motion delay. There is no motion delay differential at 1600 and 26,000 CPI, and the M75 Air in fact is slightly ahead in both cases.

Wireless Testing

Upon switching to wireless, SPI timing jitter is virtually unchanged.


Once again, 1600 and 26,000 CPI are tested. I can measure a wireless motion delay differential of roughly 1-1.5 ms, though typically 1 ms, at either step.


A rather curious behavior previously encountered on several releases from Razer (DeathAdder V2 Pro, V3 Pro, Viper V2 Pro, Naga V2 Pro, among others) and a few other manufacturers such as VAXEE is present on the M75 Air as well. At any point during the motion, though typically at the start, motion delay is increased by a single interval (i.e., 1 ms), which is maintained through the motion. From what I can tell, this only happens in wireless (2.4 GHz) operation. I'm unable to reproduce this behavior consistently.


Upon closer inspection, it becomes clear that any of these shifts correlates with an off-period poll.

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

Considering the M75 Air is usable as a wired mouse as well, I'll be testing polling rate stability for both wired and wireless use.

Wired Testing


All of the available polling rates (125, 250, 500, and 1000 Hz) look and perform fine.

Wireless Testing
For wired mice, polling rate stability merely concerns the wired connection between the mouse (SPI communication) and 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 being out of sync would be indicated by at least one 2 ms report, which would be the result of any desynchronization drift accumulated over time. I'm able to detect periodic off-period polls, which may be related to a desynchronization drift.



Second, I'm testing the general polling-rate stability of the individual polling rates in wireless mode. Running the M75 Air at a lower polling rate can have the benefit of extending battery life. All of the available polling rates are performing fine, with the exception of 1000 Hz, which shows regular 2 ms polls along with generally increased noise.

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 CPI. 16,000 CPI shows significant jitter, which is amplified to major levels at 26,000 CPI. This is in line with what to expect from a sensor lacking smoothing entirely or almost entirely. Lastly, there is no sensor lens movement.

Lift-off Distance

The M75 Air offers three pre-defined LOD levels to choose from. Using the "Low" setting, the sensor does not track at a height of 1 DVD (<1.2 mm). Using either the "medium" or "high" setting, the sensor does track at a height of 1 DVD, but not at a height of 2 DVDs (1.2<x<2.4 mm; x=LOD height). Furthermore, one can perform a surface calibration, which may lower LOD beyond the lowest level. 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, debouncing is required to avoid double clicks, slam-clicks, or other unintended effects of switch bouncing. Debouncing typically adds a delay, which, along with any potential processing delay, shall be referred to as click latency. In order to measure click latency, the mouse has been interfaced with an NVIDIA LDAT (Latency Display Analysis Tool). Many thanks go to NVIDIA for providing an LDAT device. More specifically, the LDAT measures the time between the electrical activation of the left main button and the OS receiving the button-down message. Unless noted otherwise, the values presented in the graph refer to the lowest click latency possible on the mouse in question. If a comparison mouse is capable of both wired and wireless operation, only the result for wireless (2.4 GHz) operation will be listed.

In wired mode and with BRO (Button Response Optimization) disabled, click latency has been measured to be 0.6 ms, with standard deviation being 0.27 ms. In wired mode and with BRO enabled, click latency has been measured to be 9.4 ms, with standard deviation being 0.32 ms. In wireless mode and with BRO disabled, click latency has been measured to be 1.0 ms, with standard deviation being 0.40 ms. Finally, in wireless mode and with BRO enabled, click latency has been measured to be 10.1 ms, with standard deviation being 0.30 ms. Furthermore, I've found Reflex reporting to be inaccurate, as the reported and measured values did not match for wireless operation with BRO enabled.