The inverse square law states that the intensity of the light from a point source diminishes inversely to the square of the distance. I=1/d² Here is a better illustration that what I drew on the white board.
I got this next chart from Lee Varis's website. He illustrates here the relationship of 18% grey to a modified 10 step zone system, 50% that you would see in Lightroom's histogram and the number 118 you see in Photoshop's histogram using RGB color space.
Here is the results of our test in class with the middle grey card adjusted in Lightroom and tweaked in photoshop to look the same. You can see the Front card gets darker in relation to the Middle card as the light is moved further away and the Back card gets lighter as the light is moved further away. The 32 foot distance looks light some other light was contaminating the results.
Here is a chart of mathematical calculations we made alone with the meter reading that actually was more accurate. I have had this experiment work in the past but not on our day. The PM's class was behaving similarly to ours. I don't have an explanation as of yet.
Production Stills by Ann Beeke
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