The Munsell Vision Test is reliant on a wide assortment of environmental factors to generate accurate and consistent color vision results. Many of these factors are universal across both physical and digital releases of the test, although several are unique to either test in their own right. The
CIE has determined some baseline values and experimental standards to be used in both editions of the test, others are fluid and merely require consistency from test to test.
Illuminants Illuminants are unique location to location across the globe, however several types of illuminant have been standardized by the
CIE. Illuminants types
D65 and
D50 are acceptable for use, however
D50 illuminant is suggested for a
calibrated and accurate color vision test result. Use of different illuminant can sway results in a significant manner due to the
spectral power distribution of alternate sources and their
incident effect on how displayed information is processed by the human visual system. Illuminants containing varying concentrations of differing
wavelength intensity light skews the
representation of color on the screen in a manner that would cause the eye to mismatch color patches. In combination with the
spatial acuity function of the human visual system,
illumination plays a significant role in the
color accuracy of a display.
Screen calibration Combined with
ambient illumination of the scene, several other factors are also integral for testing environment standardization.
Calculated screen gamma is a significant factor. As gamma changes for the display, the representation of
color,
contrast and
saturation are affected proportional to the magnitude of the change of the gamma curve. CIE recommends a gamma value of 2.2 as it is the current display manufacturing standard. A proper, professional grade screen calibration is required in order for concretely accurate test information. Several companies manufacture portable display calibration tools. Tools such as these take into account the type of screen and the screen's primary illumination source. There is no standard monitor hardware specification for the digital release of the Munsell Vision Test. Correct and thorough monitor calibration takes into account human visual system
metamerism, a phenomenon that combines several color science elements to generate
visual matching colors regardless of differences in source illumination, although it is ultimately not universally effective.
Formal monitor tests Informative subject testing done at the
Rochester Institute of Technology's Munsell Color Science Lab discovered consistent
color perception difficulties when identical subjects performed the Munsell Vision Test on varying calibrated monitors in a test comparing color vision test results between
Apple MacBook Pro laptop displays and a
Samsung LCD Monitor. Results garnered from the experiment exemplified the differences that displays can exhibit in failure to accurately quantify color.
Incident angle to the test monitor is a final strong source of
experimental uncertainty, as very few monitors commercially available are capable of accurately representing
hue,
tone and
saturation consistently at all viewing angles incident to the monitor.
Observer error Several sources of error (and therefore, inherent accuracy shortcomings) are directly related to the observer. Although CIE demonstrates several sets of data regarding the optimal, standard observer, each individual observer differs slightly from the baseline. Factors like
visual acuity, color blindness and visual system defects (
cataracts, surgeries,
LASIK,
tinted optics,
poor cone responsivity, etc.) are all directly tied to observer color perception accuracy. The accuracy of an observers test answers are represented in Test Results == Test results and interpretation ==