Image 02


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    : 2005:08:04 14:41:01
# Resolution   : 2048 x 1536 in jpeg (2064x1540 in pgm/02.pgm)
# Focal length : 11.0mm
# Exposure time: 0.004 s  (1/250)
# Aperture     : f/7.7
# 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    30    34    22    22       28.5     34.2     25.9     27.4     29.3  
 10   276   312   240   238        262      314      283      296      256  
 50  2692  2612  2170  2104       2.56E3   2.63E3   2.56E3   2.62E3   2.56E3
 90 16290 16296 15050 15016       1.55E4   1.64E4   1.77E4   1.87E4   1.48E4
 99 16316 16316 16318 16316       1.55E4   1.64E4   1.92E4   2.03E4   1.44E4
100 16346 16344 16352 16344       1.55E4   1.65E4   1.93E4   2.03E4   1.44E4
# flux from 4.68 sr ( 9.03E-6 sr/4px) is  1.14E4 lx (SQM 3.58E3 nt,  3.70 mag);
# tilewise luminance  4.66E3 cd/m2 with rel. SD 99.6 % (summing pixels below 16380)
# dark frame dark/off.pgm subtracted from all values
# Yell average=4467.3  minimum=  -42  maximum=16346   over 16380: 62120
# Cyan average=4355.7  minimum=  -40  maximum=16344   over 16380: 60348
# Gree average=4262.6  minimum=  -72  maximum=16352   over 16380: 88456
# Mage average=4263.4  minimum=  -50  maximum=16344   over 16380: 112475

End of results of "raw2lum" (version 1.22) with parameters:
  -c YCGM -fa -w 7.3 -fc0.214 -o 16380 -d dark/off.pgm -sm200 -nh -i 02.txt -e 02.eps -n 02.ppm -t156 -c 3412 -s64 pgm/02.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)