Image 51


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 03:06:05
# Resolution   : 1280 x 960 in jpeg (1424x1076 in pgm/51.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   -22   -22   -21   -42        -0.00632  -0.00357  -0.0110  -0.00453
 10    28    22    23    -4         0.00805   0.00374  -0.00104   0.00525
 50   193   166   167    52         0.0555   0.0277   0.0136   0.0374
 90  2401  1756  1756   241         0.690    0.292    0.0628   0.431 
 99  3649  2653  2657   387         1.05     0.441    0.101    0.654 
100  8838  5739  6564   806         2.54     1.02     0.210    1.55  
# flux from 0.654*0.98 sr ( 8.59E-7 sr/4px) is  0.0807 lx ( 0.0824 lx tilewise);
# tilewise luminance  0.154 cd/m2 with rel. SD  118 % (summing pixels below 15850 and with non-zero green: there is 97.9 % of them)
# Fuji Devignetting: 1 # dark frame dark/43.pgm subtracted from all values
# Red  average= 710.7  minimum= -172  maximum= 8838   over 15850:   0 zero:  1.3 %
# GrUp average= 542.5  minimum= -105  maximum= 5739   over 15850:   0 zero:  2.2 %
# GrDw average= 542.3  minimum= -104  maximum= 6564   over 15850:   0 zero:  2.1 %
# Blue average=  90.6  minimum= -130  maximum=  806   over 15850:   0 zero:  8.7 %

End of results of "raw2lum" (version 1.22) with parameters:
  -c fuji -fa -d dark/43.pgm -sm100 -nh -nt -i 51.txt -e 51.eps -n 51.ppm -t 118 -s71:76 pgm/51.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)