Image 12


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 00:37:19
# Resolution   : 2048 x 1536 in jpeg (2064x1540 in pgm/12.pgm)
# Focal length :  8.2mm
# Exposure time: 0.008 s  (1/125)
# 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   -36   -38   -46   -40      -1.67    -1.87    -2.65    -2.44    -1.38  
 10   -20   -20   -24   -20      -0.930   -0.986   -1.38    -1.22    -0.794 
 50     2     0     2     2       0.0930   0.00     0.115    0.122    0.0863
 90    24    22    26    24       1.12     1.08     1.50     1.46     1.00  
 99    50    42    50    48       2.33     2.07     2.88     2.92     2.16  
100 16324 16322 16334 16322        759      805      942      994      704  
# flux from 0.528 sr ( 7.01E-7 sr/4px) is  0.122 lx;
# tilewise luminance  0.234 cd/m2 with rel. SD  516 % (summing pixels below 16380)
# dark frame dark/off.pgm subtracted from all values
# Yell average=   5.1  minimum=  -82  maximum=16324   over 16380:  92
# Cyan average=   3.0  minimum=  -84  maximum=16322   over 16380: 139
# Gree average=   3.5  minimum=  -94  maximum=16334   over 16380: 175
# Mage average=   4.6  minimum=  -94  maximum=16322   over 16380:  87

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 12.txt -e 12.eps -n 12.ppm -t168 -c 3412 -s64 pgm/12.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)