Thank you Photo Engineer , Autochrome uses RGB and when it is scanned , it makes flat histogram.
But when thinking ,
What about digital cameras , they use RGB pixels and by this way , they should aim to give flat histograms but this is not true.
Which is false ?
When scanned, digital data is sending the fact that it is RGB. Analog data is sending the fact that it is CMY (K). I think that the information transmitted may be critical.