Image 38

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 01:18:02
# Resolution   : 2048 x 1536 in jpeg (2064x1540 in pgm/38.pgm)
# Focal length :  8.2mm
# Exposure time:60.120 s 
# Aperture     : f/2.5
# 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   -35   -33   -43   -37      -2.33E-4  -2.33E-4  -3.55E-4  -3.23E-4  -1.97E-4
 10   -12   -12   -16   -15      -8.00E-5  -8.48E-5  -1.32E-4  -1.31E-4  -6.43E-5
 50    23    19    24    21       1.53E-4   1.34E-4   1.98E-4   1.83E-4   1.40E-4
 90   116    91    93    92       7.73E-4   6.43E-4   7.68E-4   8.03E-4   7.74E-4
 99   321   193   204   221       0.00214   0.00136   0.00169   0.00193   0.00228
100 16299 16296 16301 16292       0.109    0.115    0.135    0.142    0.101 
# flux from 6.28 sr ( 1.62E-5 sr/4px) is  0.00211 lx (SQM 8.09E-4 nt, 20.31 mag);
# tilewise luminance  2.88E-4 cd/m2 with rel. SD  149 % (summing pixels below 16380)
# dark frame dark/1m.pgm subtracted from all values
# Yell average=  44.3  minimum= -512  maximum=16299   over 16380:  33
# Cyan average=  32.2  minimum= -465  maximum=16296   over 16380:  38
# Gree average=  34.2  minimum= -512  maximum=16301   over 16380:  37
# Mage average=  33.8  minimum= -512  maximum=16292   over 16380:  32

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 38.txt -e 38.eps -n 38.ppm -t156 -c 3412 -s64 pgm/38.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)