Brightness and whiteness are not the same thing. Brightness is the measure of the amount of light reflected from the surface of a sheet of paper -the quantity of light. Whiteness, on the other hand, is how light is reflected within the visible range of the spectrum -the quality of light.
How is Brightness Measured?
TAPPI, the Technical Association for the Pulp and Paper Industry, rates brightness on a scale from 0 -100. The higher the rating, the brighter the paper. The brighter the paper, the greater the contrast between paper and image and the greater the color intensity. The human eye cannot accurately assess brightness. Shade, finish, gloss, and other factors confuse the eye.
How Does Whiteness Affect Print Results?
Whiteness depends upon how a sheet of paper reflects color back to the eye. A blue-white sheet of paper reflects more light within the blue/violet range of the visible spectrum, and is an excellent choice for printing cool colors like blues and blacks and for contrast. The human eye often perceives blue-whites to be brighter than they really are. Warm whites reflect more within the red/orange range of the visible spectrum and are an excellent choice for printing warm colors such as flesh tones and for ease of reading. Balanced (neutral) whites reflect all colors in the visible spectrum equally and provide accurate color reproduction.