Allan, I rarely actually use it, but if I really want to know the relative relationships between certain values, all I have to do is hold the gray-scale circle against the value I wish to get a reading of and rotate it until I discern a value match. It fits nicely in my hand, measuring 6.5 inches or 16.7 cm in diameter. The numbers are meant to correspond with the L.a.b. scale.

Leslie, it does not really need any holes to read through, although I like your idea on your own design.

Garth

All I can say is this has been great to follow. Thanks !!