To reliably measure contrast, it is necessary to have more than just a histogram.
Contrast is driven my the Human Visual System, which has low and high cutoffs for contrast. Some say it is acuity based, but not really. One can have normal acuity and have substantially sub-normal contrast sensitivity.
Peak HVS contrast response is at 4 cycles per degree. The upper limit is about 60 cycles per degree. Perception of contrast also changes with color, and illuminance. As an example, contrast in the blue range is not as sensitive as in the yellow-green range. Also, as has been shown in lab tests with pilots, available oxygen also impacts contrast (it changes the metabolic mechanisms in the HVS affecting sensitivity).
Since the metric is closer to perceived cycles per subtended angle, viewing distance and image size will also affect contrast, with illuminance and spectral content having effects as well.
Tangential discussion: I haven't thought about it much, but it seems that one could make a contrast detector using the mechanics of image viewing, the spectral content of the image as distributed spatially. It would seem that a FFT might be a useful tool in evaluating the contrast sensitivity, but I am just talking here. Certainly FFTs are useful in determining sharpness, but that is not contrast. And that does not factor in the spectral / spatial responsivity of the HVS.
So the correct answer to the question is: A histogram alone will not universally answer the contrast grading question. Rather spatial effects (cycles per angle) as well as other factors of the HVS (illuminance, color, the condition of the lens, and other biological factors).