and recorded, These factors included: 
1. Atmospheric haze, 
2. The time of day when observations 
were taken, 
3, Azimuth and altitude of the sun with 
respect to 
a, the terrain 
b. the observer's line of sight 
e, the orientation of the face of the 
object in view 
4, Viewing distance, 
These data are intended to contribute to continuing 
study of the effects of these and other factors, This study 
must ultimately include information from many physiographic 
and climatic areas before reliable conclusions can be reached, 
The limited data now in hand, however, indicate that: 
1l. The colors of hand specimens of rock are 
more vivid than the colors of larger 
areas of these same rocks viewed at 
distances exceeding 300 feet. 
Different observers, using the Munsell 
system of color notation, may obtain 
different color-match determinations 
under similar conditions. 
True color representation 1s not neces- 
sarily essential to the use of color 
photographs for geologic study. 
A loss of color chroma and a loss of 
visual acuity take place with increases 
in viewing distances. Atmospheric haze, 
however, not viewing distance, 1s the 
primary cause of these losses, 
The effects of atmospheric haze are more 
pronounced in the valley areas than in 
the uplands, (In valley areas some 
color differences known to be present 
could not be detected at viewing 
distances of approximately two miles.)