The Ruby Beholder tool helps you find light, medium, and dark value in colors. The tool is designed to mask fabric colors, so you see only relative values. Now you can easily sort fabrics for a project and get just the right contrast between fabrics before you sew. No more muddy quilts! The Ruby Beholder is also used by painters, photographers, and more. Learn more about the Ruby Beholder tool here: http://www.shopmartingale.com/ruby-be...