Image 29


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 02:49:49
# Resolution   : 1280 x 960 in jpeg (1424x1076 in pgm/29.pgm)
# Focal length :  7.5mm  (35mm equivalent: 51mm)
# 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   -50   -46   -47   -52        -0.0575  -0.0309  -0.0542  -0.0402
 10   -17   -15   -15   -22        -0.0195  -0.00997  -0.0229  -0.0133
 50    26    24    24     7         0.0299   0.0159   0.00730   0.0208
 90   155   143   143    60         0.178    0.0950   0.0626   0.124 
 99   544   422   425   116         0.625    0.281    0.121    0.402 
100 15869 15866 15866 15867         18.2     10.5     16.6     13.2  
# flux from 0.379*0.77 sr ( 4.96E-7 sr/4px) is  0.0187 lx ( 0.0227 lx tilewise);
# tilewise luminance  0.0622 cd/m2 with rel. SD  150 % (summing pixels below 15850 and with non-zero green: there is 76.8 % of them)
# Fuji Devignetting: 1 # dark frame dark/42.pgm subtracted from all values
# Red  average=  81.3  minimum= -143  maximum=15869   over 15850: 451 zero: 20.8 %
# GrUp average=  75.4  minimum= -119  maximum=15866   over 15850: 373 zero: 23.2 %
# GrDw average=  74.9  minimum= -114  maximum=15866   over 15850: 374 zero: 23.2 %
# Blue average=  26.3  minimum= -123  maximum=15867   over 15850:  86 zero: 30.6 %

End of results of "raw2lum" (version 1.22) with parameters:
  -c fuji -fa -d dark/42.pgm -sm100 -nh -nt -i 29.txt -e 29.eps -n 29.ppm -t 118 -s71:76 pgm/29.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)