A practical question about the in-camera raw histogram if there was such a thing, how would one use it? It would still have to be displayed on a scale so in order to know what is going on beyond this scale, one would need some way to handle the histogram as you would in CameraRaw or Lr. Kind of awkward fidgeting with the camera display trying to figure out if you nailed the ETTR while shooting on location. No?
My preferred format would be log X axis (with EV divisions) + linear Y axis. Histograms like this would be tremendously intuitive giving precise information about the adjustments needed for accurate optimum exposure (ETTR):
![](https://4.bp.blogspot.com/-XIK2EOPW3C4/WvIWVVwKG1I/AAAAAAAADdE/7HWZgFkIsCYBw5iPdWhnmplP0ZlB7uG3ACLcBGAs/s1600/histogramaraw1.png)
Just a glance to find out that adding +1,5EV means perfect ETTR here. Or just +1EV if you don't even want to sacrifice those very few G photosites.
Such histogram also provides a precise DR measurement of the scene; 8 stops in this case (number of vertical divisions with relevant content). A camera with N-bit RAW files encoding can
measure DR of up to N stops, no matter if the sensor's
capture DR is lower than N stops.
Regards