Image 01


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 02:22:02
# Resolution   : 1280 x 960 in jpeg (1424x1076 in pgm/01.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   -60   -53   -53   -59        -0.0172  -0.00880  -0.0154  -0.0118
 10   -29   -24   -25   -28        -0.00833  -0.00407  -0.00730  -0.00556
 50     0     0     0     0         0.00     0.00     0.00     0.00  
 90    45    41    42    42         0.0129   0.00689   0.0110   0.00901
 99    82    78    78    78         0.0236   0.0130   0.0203   0.0167
100 15869 15866 15866 15867         4.56     2.64     4.14     3.31  
# flux from 0.654*0.58 sr ( 8.59E-7 sr/4px) is  9.09E-4 lx ( 0.00159 lx tilewise);
# tilewise luminance  0.00246 cd/m2 with rel. SD  102 % (summing pixels below 15850 and with non-zero green: there is 58.2 % of them)
# Fuji Devignetting: 1 # dark frame dark/43.pgm subtracted from all values
# Red  average=  10.7  minimum= -344  maximum=15869   over 15850:  11 zero: 35.5 %
# GrUp average=  11.7  minimum= -144  maximum=15866   over 15850:   7 zero: 42.1 %
# GrDw average=  12.1  minimum= -134  maximum=15866   over 15850:  14 zero: 41.4 %
# Blue average=   8.2  minimum= -372  maximum=15867   over 15850:   5 zero: 39.3 %

End of results of "raw2lum" (version 1.22) with parameters:
  -c fuji -fa -d dark/43.pgm -sm100 -nh -nt -i 01.txt -e 01.eps -n 01.ppm -t 118 -s71:76 pgm/01.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)