Image 02


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 02:22:32
# Resolution   : 1280 x 960 in jpeg (1424x1076 in pgm/02.pgm)
# Focal length :  5.7mm  (35mm equivalent: 39mm)
# CCD width    : 5.32mm
# Exposure time: 2.000 s 
# 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)* 1.66E-4
# %    R     G1    G2    B readings  R        G        B        L / cd/m2
  1   -59   -53   -53   -59        -0.0170  -0.00880  -0.0154  -0.0117
 10   -29   -24   -24   -28        -0.00833  -0.00399  -0.00730  -0.00551
 50     0     0     0     0         0.00     0.00     0.00     0.00  
 90    46    43    44    43         0.0132   0.00723   0.0112   0.00932
 99    85    80    80    79         0.0244   0.0133   0.0206   0.0172
100 15869 15866 15866  1635         4.56     2.64     0.426    3.31  
# flux from 0.654*0.60 sr ( 8.59E-7 sr/4px) is  0.00103 lx ( 0.00169 lx tilewise);
# tilewise luminance  0.00268 cd/m2 with rel. SD  125 % (summing pixels below 15850 and with non-zero green: there is 59.9 % of them)
# Fuji Devignetting: 1 # dark frame dark/43.pgm subtracted from all values
# Red  average=  11.9  minimum= -338  maximum=15869   over 15850:   3 zero: 34.1 %
# GrUp average=  12.8  minimum= -119  maximum=15866   over 15850:   1 zero: 40.2 %
# GrDw average=  13.0  minimum= -119  maximum=15866   over 15850:   2 zero: 39.9 %
# Blue average=   8.9  minimum= -372  maximum= 1635   over 15850:   0 zero: 38.1 %

End of results of "raw2lum" (version 1.22) with parameters:
  -c fuji -fa -d dark/43.pgm -sm100 -nh -nt -i 02.txt -e 02.eps -n 02.ppm -t 118 -s71:76 pgm/02.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)