Image 30


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 02:50:05
# Resolution   : 1280 x 960 in jpeg (1424x1076 in pgm/30.pgm)
# Focal length : 27.9mm  (35mm equivalent: 189mm)
# CCD width    : 5.32mm
# Exposure time: 0.500 s  (1/2)
# Aperture     : f/3.2
# ISO equiv.   : 200

# Selected image percentils         L=(1.730*0.35*R+1.000*0.65*G+1.570*0.00*B)* 8.68E-4
# %    R     G1    G2    B readings  R        G        B        L / cd/m2
  1   -46   -43   -44   -51        -0.0691  -0.0377  -0.0695  -0.0487
 10   -11    -9    -9   -20        -0.0165  -0.00781  -0.0272  -0.0109
 50    50    45    46    13         0.0751   0.0395   0.0177   0.0519
 90   399   308   308    72         0.599    0.267    0.0981   0.383 
 99  1029   767   771   136         1.54     0.667    0.185    0.974 
100 15869 15866 15866 15867         23.8     13.8     21.6     17.3  
# flux from 0.0275*0.82 sr ( 3.59E-8 sr/4px) is  0.00381 lx ( 0.00428 lx tilewise);
# tilewise luminance  0.151 cd/m2 with rel. SD  103 % (summing pixels below 15850 and with non-zero green: there is 82.3 % of them)
# Fuji Devignetting: 2 # dark frame dark/42.pgm subtracted from all values
# Red  average= 170.8  minimum= -117  maximum=15869   over 15850: 392 zero: 15.5 %
# GrUp average= 139.3  minimum= -126  maximum=15866   over 15850: 313 zero: 18.0 %
# GrDw average= 138.2  minimum= -123  maximum=15866   over 15850: 301 zero: 17.5 %
# Blue average=  32.2  minimum= -120  maximum=15867   over 15850: 108 zero: 26.7 %

End of results of "raw2lum" (version 1.22) with parameters:
  -c fuji -fa -d dark/42.pgm -sm100 -nh -nt -i 30.txt -e 30.eps -n 30.ppm -t 118 -s71:76 pgm/30.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)