QUANTITATIVE PHOTOGRAPHY— A GEOLOGIC RESEARCH TOOL 
50r 
Rock unit A 
— 
Pm 
" 
40} / e 
/ Rock unit B a 
A i Rock unit C 
REFLECTANCE 
% 
  
  
L i i i 
LL i 
400 450 500 550 600 650 700 
WAVELENGTH IN MILLIMICRONS 
FrG. 4. Spectral reflectance curves of fresh samples of light-brown sandstone (4), gray limestone (B), 
red shaly siltstone (C), and gray sandstone (D). See photographs of samples in Figures 5 and 6. 
  
FrG. 5. Photograph of fresh samples of light- FrG. 6. Photograph of fresh samples of light- 
| brown sandstone (4), gray limestone (B), red shaly brown sandstone (4), gray limestone (B), red shaly 
siltstone (C), and gray sandstone (D) taken through siltstone (C), and gray sandstone (D) taken through 
a combination of No. 8 and 47 Wratten filters on a No. 25 Wratten filter on panchromatic film. Note 
panchromatic film. Note that sample of rock unit that sample of rock unit 4 is light toned; others are 
| C is dark toned; others are relatively light toned. relatively dark toned. Contrast Figure 5. 
| Contrast Figure 6.