AN ABRIDGED TECHNIQUE TO DIAGNOSE SPECTROPHOTOMETRIC ERRORS

The effect on colorimetric accuracy of spectrophotometric errors (+/- 0.5 and +/- 1% reference white, +/- 0.25 and +/- 0.5% reference black, and +/- 0.5 and +/- 1 nm wavelength) was simulated for the BCRA Sei-i es II tile set by using previously investigated models for these error s. Delta E(94) color differences of up to 5.2 could result. Because t he errors are linearly related to CIELAB differences for each tile, a technique was derived that enabled Delta L Delta a*, and Delta b* coo rdinates between a calibrated tile and its measured value to be transf ormed into estimates of reference white, reference black, and waveleng th error. The cyan tile was identified as the most effective tile for this technique. ''Universal'' equations are included for 45/Normal and Normal/Total geometries traceable to the National Institute of Standa rds and Technology (NIST), and Normal/45, Normal/Total, and Normal/Dif fuse geometries traceable to the National Physical Laboratory (NPL). M easuring the cyan tile on a regular basis and transforming its colorim etric coordinates into spectrophotometric error metrics provides a use ful method to validate the accuracy and reproducibility of a color-mea surement instrument. (C) 1997 John Wiley & Sons, Inc.