Image 14


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 00:37:49
# Resolution   : 2048 x 1536 in jpeg (2064x1540 in pgm/14.pgm)
# Focal length :  8.2mm
# Exposure time: 2.000 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    -8   -16   -24   -16      -0.00149  -0.00315  -0.00554  -0.00390  -2.74E-4
 10    28     8     8    16       0.00521   0.00158   0.00185   0.00390   0.00622
 50   132    72    76    88       0.0246   0.0142   0.0175   0.0214   0.0267
 90  1172   456   508   800       0.218    0.0899   0.117    0.195    0.248 
 99  7216  2948  3236  5012       1.34     0.581    0.746    1.22     1.52  
100 16356 16336 16352 16348       3.04     3.22     3.77     3.98     2.82  
# flux from 0.525 sr ( 7.01E-7 sr/4px) is  0.0499 lx;
# tilewise luminance  0.0999 cd/m2 with rel. SD  126 % (summing pixels below 16380)
# dark frame dark/2s.pgm subtracted from all values
# Yell average= 484.2  minimum=  -64  maximum=16356   over 16380: 1996
# Cyan average= 227.8  minimum= -180  maximum=16336   over 16380: 3119
# Gree average= 246.7  minimum= -164  maximum=16352   over 16380: 4250
# Mage average= 348.3  minimum= -144  maximum=16348   over 16380: 1766

End of results of "raw2lum" (version 1.22) with parameters:
  -c YCGM -fa -w 7.3 -fc1.03 -o 16380 -d dark/2s.pgm -sm200 -nh -i 14.txt -e 14.eps -n 14.ppm -t168 -c 3412 -s64 pgm/14.pgm

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)