Color-value Isolator
This color-value isolator is almost exactly a middle
value. Print the isolator, then cut out a 3/4 inch hole in the
middle.
Card stock works best but regular printer paper will do just
fine.
To use, close one eye and
look at your subject through the hole in the center. As you move
the isolator around the subject, dark values will be darker
than the isolator, light values will be lighter and middle values will
closely match.
When using the isolator to find notan, all areas which appear darker
than the isolator belong on the dark side of notan. Once the
darks are placed, the lights in the notan drawing take care of
themselves. Areas which exactly match the isolator can belong to
either side. I usually leave them light if the composition is
strongly lit, but place them with the darks if the composition is in low
light.
