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I understand the basic logic of providing histograms of JPEGs. The sensor pixel values get combined, processed, interpreted as a color, then broken out into new RGB values. So, if you were to give the red histogram of the sensor, it would be different than the red histogram of the JPEG, so it would not represent the color mix accurately. I get that.
However, most of the time, I am not using the histogram to interpret color, I want to use it to determine whether my sensor is being saturated (or underexposed). The histogram for the sensor would be useful for that.
In other words, let's say the max value for the sensor pixel is 256, and one of the pixels registers a 256, but ends up getting a value of 254 in the resulting JPEG. So, the camera is saying "oh look the pixel is not saturated anymore". Well, I don't care that the camera decreased the value after the fact. I want to know if the sensor pixel was saturated originally. I want to know if the "sensor well" is full or not.
This would seem to be an obvious feature, but for some reason even the most expensive cameras seem to only provide JPEG histograms. Am I missing something here, or is this just a blind spot in current functionality designs?