Image 17

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 02:37:28
# Resolution   : 1280 x 960 in jpeg (1424x1076 in pgm/17.pgm)
# Focal length :  5.7mm  (35mm equivalent: 39mm)
# CCD width    : 5.32mm
# Exposure time: 2.000 s 
# Aperture     : f/2.8
# ISO equiv.   : 200

# Selected image percentils         L=(1.730*0.35*R+1.000*0.65*G+1.570*0.00*B)* 1.66E-4
# %    R     G1    G2    B readings  R        G        B        L / cd/m2
  1   -59   -53   -53   -57        -0.0170  -0.00880  -0.0149  -0.0117
 10   -28   -24   -24   -27        -0.00805  -0.00399  -0.00704  -0.00541
 50     1     0     0     0         2.87E-4   0.00     0.00     1.00E-4
 90    47    43    43    44         0.0135   0.00714   0.0115   0.00937
 99    91    84    84    84         0.0261   0.0140   0.0219   0.0182
100 15869 15866 15866 15859         4.56     2.64     4.14     3.31  
# flux from 0.654*0.60 sr ( 8.59E-7 sr/4px) is  0.00141 lx ( 0.00232 lx tilewise);
# tilewise luminance  0.00345 cd/m2 with rel. SD  186 % (summing pixels below 15850 and with non-zero green: there is 59.7 % of them)
# Fuji Devignetting: 1 # dark frame dark/43.pgm subtracted from all values
# Red  average=  17.2  minimum= -331  maximum=15869   over 15850:  23 zero: 33.6 %
# GrUp average=  16.8  minimum= -115  maximum=15866   over 15850:  24 zero: 40.4 %
# GrDw average=  16.9  minimum= -119  maximum=15866   over 15850:  12 zero: 40.2 %
# Blue average=  11.0  minimum= -372  maximum=15859   over 15850:   2 zero: 36.8 %

End of results of "raw2lum" (version 1.22) with parameters:
  -c fuji -fa -d dark/43.pgm -sm100 -nh -nt -i 17.txt -e 17.eps -n 17.ppm -t 118 -s71:76 pgm/17.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)