Image 55


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 03:07:53
# Resolution   : 1280 x 960 in jpeg (1424x1076 in pgm/55.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   -55   -51   -50   -54        -0.0158  -0.00839  -0.0141  -0.0110
 10   -24   -20   -20   -23        -0.00690  -0.00332  -0.00600  -0.00457
 50    12    12    12    10         0.00345   0.00199   0.00261   0.00250
 90    69    70    71    63         0.0198   0.0117   0.0164   0.0146
 99   589   461   455   120         0.169    0.0761   0.0313   0.109 
100 15869 15866 15866 15867         4.56     2.64     4.14     3.31  
# flux from 0.654*0.72 sr ( 8.59E-7 sr/4px) is  0.00447 lx ( 0.00583 lx tilewise);
# tilewise luminance  0.00839 cd/m2 with rel. SD  223 % (summing pixels below 15850 and with non-zero green: there is 71.8 % of them)
# Fuji Devignetting: 1 # dark frame dark/43.pgm subtracted from all values
# Red  average=  46.5  minimum= -310  maximum=15869   over 15850:  18 zero: 24.7 %
# GrUp average=  44.3  minimum= -115  maximum=15866   over 15850:  14 zero: 28.5 %
# GrDw average=  44.1  minimum= -112  maximum=15866   over 15850:  17 zero: 28.0 %
# Blue average=  23.5  minimum= -345  maximum=15867   over 15850:   9 zero: 27.0 %

End of results of "raw2lum" (version 1.22) with parameters:
  -c fuji -fa -d dark/43.pgm -sm100 -nh -nt -i 55.txt -e 55.eps -n 55.ppm -t 118 -s71:76 pgm/55.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)