Bright strongly metameric visually matching pairs of white lights are studied. Generally one member of the pair is a constant broadband reference white, in accordance with the Maxwell method. Spectral compositions of the other member are chosen from eight types found in Parts I, II, and III to lead to tristimulus errors, over a large range of magnitude, by the 1964 CIE Standard Observer. Field luminance has been tripled over that of the earlier work to the order of 100 cd/m(2), the range of typical industrial color-matching Experiments with visual fields of 1.3 degrees have been added. Tristimulus errors in computations by the appropriate CIE Standard Observer, at the higher brightness levels, and at visual field sizes of both 10 degrees and 1.3 degrees, are as large as those found in the earlier work with dimmer 10 degrees fields.