[Sean_D]

… folks were posting all kinds of equations that just made my head spin.

Reminds me of one I saw that had to do with determining the optimal focal length for your DSLR camera for portraiture based on sensor size. Something along the lines of … determine the length and width of the sensor. Square each number. Add the two results and then find the square root of that number. Whatever that number is double it and that will give you the correct focal length to use with your camera for portraits. Seriously? Who thinks up these things? Do they just wake bolt upright in the middle of the night with some kind of epiphany? LOL