Photoshop value experiments

I have trouble with values, figuring out how dark is dark etc. Relative value I can manage, absolute value is a problem.

I just tried this experiment, and I think it works. Please note the quality, brightness, and contrast of your reference photo will make a significant difference.

Open the attached file in Photoshop. Change the tool to eyedropper, and change the sliders to HSB. Try to guess what the value of an area is, say the deepest part of the eyebrow on the lighted side. Sample with the eyedropper, and the numerical value/10 of the bottom slider in Photoshop, the balance slider, is the value.

I was surprised to find that the deepest value on the lighted side is about a 4. Even the deepest part of the nostril is a 6. On the shadow side, the deepest values are in the pit of the eye and the upper corner of the forehead where it meets the hairline, about a 3.5.

For study I think this is pretty interesting. I hope someone else here finds it useful too.