Image 26

original 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    : 2005:08:05 01:07:31
# Resolution   : 2048 x 1536 in jpeg (2064x1540 in pgm/26.pgm)
# Focal length : 15.2mm
# Exposure time:60.120 s 
# Aperture     : f/3.2
# ISO equiv.   : 100

#c li count  min   Yav   max  ovf   min  Cav    max   ovf   min  Gav    max   ovf   min  Mav   max   ovf
# %    Y     C     G     M readings  Y        C        G        M        L / cd/m2
  1   -31   -35   -73   -64      -3.38E-4  -4.05E-4  -9.88E-4  -9.15E-4  -1.44E-4
 10    -7   -11   -24   -20      -7.64E-5  -1.27E-4  -3.25E-4  -2.86E-4  -1.88E-6
 50    32    24    17    17       3.49E-4   2.78E-4   2.30E-4   2.43E-4   3.85E-4
 90   112    79    72    75       0.00122   9.14E-4   9.75E-4   0.00107   0.00130
 99   240   147   145   159       0.00262   0.00170   0.00196   0.00227   0.00282
100 16309 16308 16304 16308       0.178    0.189    0.221    0.233    0.165 
# flux from 3.62 sr ( 4.73E-6 sr/4px) is  0.00182 lx (SQM 8.69E-4 nt, 20.24 mag);
# tilewise luminance  5.79E-4 cd/m2 with rel. SD  137 % (summing pixels below 16380)
# dark frame dark/1m.pgm subtracted from all values
# Yell average=  51.9  minimum= -512  maximum=16309   over 16380: 197
# Cyan average=  35.0  minimum= -512  maximum=16308   over 16380: 265
# Gree average=  26.4  minimum= -512  maximum=16304   over 16380: 295
# Mage average=  28.6  minimum= -512  maximum=16308   over 16380: 207

End of results of "raw2lum" (version 1.22) with parameters:
  -c YCGM -fa -w 7.3 -fc0.214 -o 16380 -d dark/1m.pgm -sm200 -nh -i 26.txt -e 26.eps -n 26.ppm -t156 -c 3412 -s64 pgm/26.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)