Image 28


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 02:47:47
# Resolution   : 1280 x 960 in jpeg (1424x1076 in pgm/28.pgm)
# Focal length : 13.6mm  (35mm equivalent: 92mm)
# 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   -45   -42   -43   -49        -0.0676  -0.0369  -0.0668  -0.0476
 10   -10    -8    -9   -17        -0.0150  -0.00738  -0.0232  -0.0100
 50    61    54    53    19         0.0916   0.0464   0.0259   0.0622
 90   664   496   497    88         0.997    0.431    0.120    0.629 
 99   866   657   657   148         1.30     0.570    0.202    0.826 
100 15869 15866 15866 15867         23.8     13.8     21.6     17.3  
# flux from 0.115*0.82 sr ( 1.51E-7 sr/4px) is  0.0235 lx ( 0.0252 lx tilewise);
# tilewise luminance  0.244 cd/m2 with rel. SD  108 % (summing pixels below 15850 and with non-zero green: there is 81.8 % of them)
# Fuji Devignetting: 2 # dark frame dark/42.pgm subtracted from all values
# Red  average= 254.6  minimum= -111  maximum=15869   over 15850: 121 zero: 15.7 %
# GrUp average= 199.7  minimum= -124  maximum=15866   over 15850:  88 zero: 18.1 %
# GrDw average= 199.7  minimum= -112  maximum=15866   over 15850:  89 zero: 18.2 %
# Blue average=  38.2  minimum= -119  maximum=15867   over 15850:  19 zero: 24.6 %

End of results of "raw2lum" (version 1.22) with parameters:
  -c fuji -fa -d dark/42.pgm -sm100 -nh -nt -i 28.txt -e 28.eps -n 28.ppm -t 118 -s71:76 pgm/28.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)