Imagine scene, contains red Imagine scene, contains red and blue surfaces (patches), shot via camera with color (bayer) filters. Red/Blue (pixel values) ratio on red will be much higher than R/B ratio on blue patch. This is how a color camera works. There is no way to fix it via single (per channel) gains, R/B(red) always will be higher than R/B(blue), regardless of gain used. So, demosaic (i.e. recovering of missing color values), than RGB -> grayscale conversion looks like the only way to go. -- Alex Tutubalin @LibRaw LLC reply
Imagine scene, contains red and blue surfaces (patches), shot via camera with color (bayer) filters.
Red/Blue (pixel values) ratio on red will be much higher than R/B ratio on blue patch. This is how a color camera works.
There is no way to fix it via single (per channel) gains, R/B(red) always will be higher than R/B(blue), regardless of gain used.
So, demosaic (i.e. recovering of missing color values), than RGB -> grayscale conversion looks like the only way to go.