When he wasn’t engaged in squeezing the back of his eyeball with various metal implements, Isaac Newton spent a lot of time scribing lines across a spectrum which he had arranged to fall onto his wall at Trinity College. One interesting thing he discovered was that the presence of these lines somehow allowed more colours to be seen than when they weren’t there.
If you count the distinct colours visible along the top edge of the image, it comes to perhaps five. Repeating this at the bottom edge of the image results in a count of almost twice that number. (This phenomenon may account for why stained glass windows are so vivid and why shops display different coloured garments piled under lights casting sharp shadows).
Today’s invention makes use of this 17th Century discovery (Why did anyone invent anything, before they invented ‘Intellectual Property’? -discuss ; )
During the manufacture of products, the precise amounts of any dye or surface colorant used can be controlled -if that’s important to marketability. Post production, when all you have is a swatch of material or a splash of paint, it’s much harder to find a perfect match from within a spectrum of available shades.
The delineation described above enables enhanced colour discrimination and so viewing colour samples side by side through two adjacent ‘windows,’ formed from a handheld, sharp-edged black frame, would enable significantly better matches to be achieved).