Color vision testing: an alternative 'source' of Illuminant C

The objective of this project was to evaluate an alternative procedure for administering reflective-type color vision tests. In this procedure, the tests are illuminated by a low color-temperature, 100 W, incandescent lamp (i.e. an improper illuminant) and the patient then views the illuminated test elements through an inexpensive gelatin filter placed before his eye (e.g. a Wratten 78AA costing about $4). Since the relative transmittance of this filter is quite similar to that used in the Macbeth Easel Lamp, the tests should still be valid. In fact, this alternative procedure yields test performances for normal and deficient subjects on the 100-hue, panel D-15, and AO H-R-R tests that are virtually identical to those obtained using a standard Macbeth Easel Lamp.