Most colour cameras use a Bayer Colour Filter Array (CFA). Each photosite records real photon intensity through a single colour filter — not RGB pixels.
At this stage, the data is:
Physically measured at each photosite
Free from interpolation
Statistically clean and local
This is the most information-rich form the sensor ever produces.
Demosaicing converts the CFA mosaic into RGB by interpolating missing colour values for each pixel. This process:
Blends neighbouring photosites
Correlates noise
Softens faint structure
Permanently discards original photosite data
Once demosaiced, the original sensor measurements cannot be recovered.
Luminance applied after de-mosaic can still improve images, but it can no longer operate on true sensor-space data.
CFALD works before demosaicing.
It treats CFA data as true luminance, preserving photosite-level signal and noise statistics for stacking and analysis. Colour is added later, cleanly and intentionally.
This follows the same principle used in mono LRGB imaging:
Preserve luminance first. Add colour second.