Image 19


original	lighter	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    : 2006:06:29 02:43:34
# Resolution   : 1280 x 960 in jpeg (1424x1076 in pgm/19.pgm)
# Focal length :  5.7mm  (35mm equivalent: 39mm)
# CCD width    : 5.32mm
# Exposure time: 0.500 s  (1/2)
# Aperture     : f/2.8
# ISO equiv.   : 200

# Selected image percentils         L=(1.730*0.35*R+1.000*0.65*G+1.570*0.00*B)* 6.64E-4
# %    R     G1    G2    B readings  R        G        B        L / cd/m2
  1   -53   -50   -51   -54        -0.0609  -0.0336  -0.0563  -0.0431
 10   -22   -20   -21   -24        -0.0253  -0.0136  -0.0250  -0.0177
 50    11     8     9     1         0.0126   0.00565   0.00104   0.00810
 90   103    92    92    50         0.118    0.0611   0.0522   0.0812
 99   737   565   565   107         0.847    0.375    0.112    0.540 
100 15899 15896 15896 15890         18.3     10.6     16.6     13.3  
# flux from 0.654*0.68 sr ( 8.59E-7 sr/4px) is  0.0234 lx ( 0.0285 lx tilewise);
# tilewise luminance  0.0399 cd/m2 with rel. SD  195 % (summing pixels below 15850 and with non-zero green: there is 67.7 % of them)
# Fuji Devignetting: 1 # dark frame dark/42.pgm subtracted from all values
# Red  average=  67.5  minimum= -123  maximum=15899   over 15850: 193 zero: 28.9 %
# GrUp average=  59.6  minimum= -129  maximum=15896   over 15850: 149 zero: 32.5 %
# GrDw average=  58.9  minimum= -112  maximum=15896   over 15850: 160 zero: 32.1 %
# Blue average=  17.6  minimum= -137  maximum=15890   over 15850:  52 zero: 37.4 %

End of results of "raw2lum" (version 1.22) with parameters:
  -c fuji -fa -d dark/42.pgm -sm100 -nh -nt -i 19.txt -e 19.eps -n 19.ppm -t 118 -s71:76 pgm/19.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)