Image 05


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 14:43:10
# Resolution   : 2048 x 1536 in jpeg (2064x1540 in pgm/05.pgm)
# Focal length :  8.2mm
# Exposure time: 0.017 s  (1/60)
# Aperture     : f/7.0
# 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    -8   -16   -14      -1.51    -1.60    -3.74    -3.46    -0.838 
 10    26    26    20    20       4.90     5.19     4.67     4.94     4.97  
 50  4142  3652  3250  2912        781      730      760      719      787  
 90 10152  9852  8280  8020       1.91E3   1.97E3   1.93E3   1.98E3   1.91E3
 99 12052 11892 10012  9536       2.27E3   2.37E3   2.34E3   2.35E3   2.25E3
100 16332 16328 16336 16330       3.08E3   3.26E3   3.82E3   4.03E3   2.86E3
# flux from 6.28 sr ( 1.62E-5 sr/4px) is  5.46E3 lx (SQM 1.75E3 nt,  4.47 mag);
# tilewise luminance   855 cd/m2 with rel. SD 96.5 % (summing pixels below 16380)
# dark frame dark/off.pgm subtracted from all values
# Yell average=4619.8  minimum=  -70  maximum=16332   over 16380: 276
# Cyan average=4489.2  minimum=  -70  maximum=16328   over 16380: 235
# Gree average=3767.4  minimum=  -82  maximum=16336   over 16380: 454
# Mage average=3643.2  minimum=  -70  maximum=16330   over 16380: 656

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 05.txt -e 05.eps -n 05.ppm -t156 -c 3412 -s64 pgm/05.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)