Image 15

original lighter colour coded

and with an inserted data grid:

(in the middle of tiles, median of raw G-pixels values is given, the bottom value is the tile luminance divided by one candela per square meter). 
# Date/Time    : 2006:06:29 02:37:05
# Resolution   : 1280 x 960 in jpeg (1424x1076 in pgm/15.pgm)
# Focal length : 17.2mm  (35mm equivalent: 116mm)
# CCD width    : 5.32mm
# Exposure time: 0.500 s  (1/2)
# Aperture     : f/3.2
# ISO equiv.   : 200

# Selected image percentils         L=(1.730*0.35*R+1.000*0.65*G+1.570*0.00*B)* 8.68E-4
# %    R     G1    G2    B readings  R        G        B        L / cd/m2
  1   -57   -54   -54   -55        -0.0856  -0.0469  -0.0749  -0.0604
 10   -28   -25   -26   -27        -0.0420  -0.0221  -0.0368  -0.0291
 50     0     0     0     0         0.00     0.00     0.00     0.00  
 90    43    41    41    39         0.0646   0.0356   0.0531   0.0457
 99   249   203   204    79         0.374    0.177    0.108    0.246 
100 15869 15865 15860  6252         23.8     13.8     8.52     17.3  
# flux from 0.0722*0.55 sr ( 9.44E-8 sr/4px) is  8.66E-4 lx ( 0.00133 lx tilewise);
# tilewise luminance  0.0168 cd/m2 with rel. SD  263 % (summing pixels below 15850 and with non-zero green: there is 55.2 % of them)
# Fuji Devignetting: 2 # dark frame dark/42.pgm subtracted from all values
# Red  average=  20.0  minimum= -143  maximum=15869   over 15850:  19 zero: 40.9 %
# GrUp average=  19.4  minimum= -129  maximum=15865   over 15850:   2 zero: 45.3 %
# GrDw average=  19.1  minimum= -123  maximum=15860   over 15850:   1 zero: 44.4 %
# Blue average=   8.6  minimum= -135  maximum= 6252   over 15850:   0 zero: 44.1 %

End of results of "raw2lum" (version 1.22) with parameters:
  -c fuji -fa -d dark/42.pgm -sm100 -nh -nt -i 15.txt -e 15.eps -n 15.ppm -t 118 -s71:76 pgm/15.pgm
Luminance scale / 1 cd/m<sup>2</sup>
Logarithmic luminance scale (the unit is candela per square meter) – intensities of snow illuminance in lux would be obtained by multiplying the numeric value of luminance by 3.6. For asphalt, such a coefficient is between 20 and 40 (or much less, for specular reflection of distant lamps)