Techie Metering question?

Below is gray scale. Each step =1 f/stop

You could try it, couldn't you? Find a photo for which you have a histogram display, and make a note of where the red, green and blue points are. Then shift the exposure up by exactly one stop, check the RGB points again, and assuming they have all moved by more or less the same amount, there's one stop's worth of difference.

I'd assume that the figure will be different for each photo, taking into account how well exposed it was originally, what the dynamic range is like, whether the darks, mids or highs dominate the picture, etc.

This might be oversimplifying, but if we accept Adams's Zone System scale from 0 to 10, that's 11 zones from black to white. 0 to 255 is 256 steps. 256 divided by 11 equals one stop increment.

Interesting question. It depends on the dynamic range of your camera's sensor. Putting on my thinking cap, if your dynamic range is 10 stops, then 25.5 would constitute one stop. It gets messy when you consider that each of your red, blue, and green inputs have that 0-255 range.