Image 50

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 03:05:47
# Resolution   : 1280 x 960 in jpeg (1424x1076 in pgm/50.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   -45   -40   -40   -49        -0.0129  -0.00664  -0.0128  -0.00884
 10    -7    -3    -3   -14        -0.00201  -4.98E-4  -0.00365  -0.00103
 50    74    68    68    32         0.0213   0.0113   0.00834   0.0148
 90  1577  1145  1147   163         0.453    0.190    0.0425   0.282 
 99  2289  1683  1684   265         0.658    0.280    0.0691   0.412 
100 12351  9400  9467  1595         3.55     1.57     0.416    2.26  
# flux from 0.654*0.87 sr ( 8.59E-7 sr/4px) is  0.0483 lx ( 0.0499 lx tilewise);
# tilewise luminance  0.0985 cd/m2 with rel. SD  133 % (summing pixels below 15850 and with non-zero green: there is 87.4 % of them)
# Fuji Devignetting: 1 # dark frame dark/43.pgm subtracted from all values
# Red  average= 472.9  minimum= -306  maximum=12351   over 15850:   0 zero: 10.8 %
# GrUp average= 361.5  minimum= -118  maximum= 9400   over 15850:   0 zero: 12.6 %
# GrDw average= 361.3  minimum= -119  maximum= 9467   over 15850:   0 zero: 12.5 %
# Blue average=  62.4  minimum= -333  maximum= 1595   over 15850:   0 zero: 16.3 %

End of results of "raw2lum" (version 1.22) with parameters:
  -c fuji -fa -d dark/43.pgm -sm100 -nh -nt -i 50.txt -e 50.eps -n 50.ppm -t 118 -s71:76 pgm/50.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)