Image 13


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 00:37:34
# Resolution   : 2048 x 1536 in jpeg (2064x1540 in pgm/13.pgm)
# Focal length :  8.2mm
# Exposure time: 0.125 s  (1/8)
# 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   -30   -34   -42   -36      -0.0893  -0.107   -0.155   -0.140   -0.0696
 10   -12   -16   -18   -14      -0.0357  -0.0505  -0.0664  -0.0546  -0.0265
 50    16     8    10    12       0.0476   0.0252   0.0369   0.0468   0.0508
 90    78    40    46    56       0.232    0.126    0.170    0.218    0.251 
 99   460   184   202   322       1.37     0.580    0.745    1.26     1.56  
100 16324 16328 16334 16340       48.6     51.5     60.3     63.7     45.1  
# flux from 0.527 sr ( 7.01E-7 sr/4px) is  0.0709 lx;
# tilewise luminance  0.140 cd/m2 with rel. SD  227 % (summing pixels below 16380)
# dark frame dark/off.pgm subtracted from all values
# Yell average=  43.8  minimum=  -88  maximum=16324   over 16380: 380
# Cyan average=  17.8  minimum=  -90  maximum=16328   over 16380: 414
# Gree average=  19.8  minimum=  -98  maximum=16334   over 16380: 420
# Mage average=  30.4  minimum=  -90  maximum=16340   over 16380: 387

End of results of "raw2lum" (version 1.22) with parameters:
  -c YCGM -fa -w 7.3 -fc1.03 -o 16380 -d dark/off.pgm -sm200 -nh -i 13.txt -e 13.eps -n 13.ppm -t168 -c 3412 -s64 pgm/13.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)