Extended Data Fig. 3: Intermediate steps in ColorChecker chart reconstruction from RGB photocurrent values.

We combined photocurrents from a stacked photosite into RGB channel brightness for reflected spectra from the ColorChecker patches. The photocurrents were normalized to the maximum current values for each channel. These values were subsequently rendered into an image representation of the ColorChecker. Notably, the resulting image exhibited a slight green tint (a), attributable to the larger area and higher sensitivity of the green pixel. To rectify the colour balance of the image, a grey balance procedure was employed (refer to Supplementary Note 3), leading to a reduction in the green tint (b). Furthermore, to enhance the brightness of the image, we applied a gamma correction function to de-linearize it (c). This approach accounts for the non-linearity of human visual response and display characteristics techniques⁴³. d. The normalized reference luminance of colour patches, vs. brightness calculated from R, G, and B channels of the stacked detector.