The opacity of paper can affect its color. For single-sheet measurements in particular, a change
in opacity results in a change in color. When taking color measurements in a laboratory using a
benchtop instrument, a "stack" is created by folding the paper a number of times until it appears
opaque. However, an on-line instrument viewing paper as it is manufactured can only measure a
single thickness of paper as it passes under the sensor, so the color values may be different than
those obtained from a benchtop instrument because the opacity is different.