Val,
Your point is well taken. No two units are the same. The trouble is there are many factors/variables that come into play with density. For instance, the styling, length of hair, and wave of the hair all have an impact on how the density appears. Also the lighting that the photo was taken in of course has an impact on the appearance of density. Add to that effect of the various shampoos and even water quality have an impact on hair. So does humidity levels. Leave-in conditioner? Age of hair? And of course the fact that the hair comes from various donors so that the diameter of the hair shaft always varies slightly. It's a moving target but we try to do the best we can.
Regards,
John
http://toplace.com/