Table 3.

Calibration performance across six different Pixel 4 devices.

		Pixel 4 device no.	Pixel 4 #1	Pixel 4 #2	Pixel 4 #3	Pixel 4 #4	Pixel 4 #5	Pixel 4 #6	Mean	STD
Correlation	MAE	Default automatic	0.19	0.2	0.21	0.18	0.15	0.15	0.18	0.03
		Uncalibrated linear	0.18	0.11	0.11	0.099	0.1	0.11	0.12	0.03
		Calibrated linear	0.079	0.036	0.061	0.05	0.06	0.034	0.05	0.02
	$R^2$	Default automatic	0.86	0.84	0.86	0.88	0.92	0.94	0.88	0.04
		Uncalibrated linear	0.73	0.82	0.83	0.88	0.83	0.84	0.82	0.05
		Calibrated linear	0.97	0.99	0.99	0.97	0.99	0.99	0.98	0.01
Bland-Altman	Bias	Default automatic	0.14	-0.14	$-$0.18	$-$0.094	$-$0.13	$-$0.037	$-$0.07	0.12
		Uncalibrated linear	$-$0.049	$-$0.029	$-$0.075	$-$0.0058	$-$0.049	$-$0.053	$-$0.04	0.02
		Calibrated linear	$-$0.078	$-$0.034	$-$0.058	$-$0.0095	$-$0.06	$-$0.029	$-$0.04	0.02
	LoA lower	Default automatic	$-$0.48	$-$0.51	$-$0.45	$-$0.5	$-$0.33	$-$0.37	-0.44	0.07
		Uncalibrated linear	$-$0.61	$-$0.37	$-$0.33	$-$0.31	$-$0.34	$-$0.38	$-$0.39	0.11
		Calibrated linear	$-$0.2	$-$0.11	$-$0.14	$-$0.15	$-$0.14	$-$0.097	$-$0.14	0.04
	LoA upper	Default automatic	0.76	0.22	0.08	0.31	0.07	0.3	0.29	0.25
		Uncalibrated linear	0.51	0.31	0.18	0.29	0.24	0.27	0.30	0.11
		Calibrated linear	0.047	0.038	0.028	0.13	0.016	0.04	0.05	0.04

The table presents Mean Absolute Error (MAE), $R^2$, Bias, Limits of Agreement (LoA Lower and LoA Upper) for each of the three tone mapping settings (Default Automatic, Uncalibrated Linear, and Calibrated Linear). These metrics are used to assess the calibration technique’s effectiveness in improving the accuracy of cPPG measurements across multiple devices of the same model. Mean and standard deviation (STD) values are also included.