Image 39


original	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    : 2005:08:05 01:20:49
# Resolution   : 2048 x 1536 in jpeg (2064x1540 in pgm/39.pgm)
# Focal length :  8.2mm
# Exposure time:60.120 s 
# Aperture     : f/2.5
# ISO equiv.   : 100

#c li count  min   Yav   max  ovf   min  Cav    max   ovf   min  Gav    max   ovf   min  Mav   max   ovf
# %    Y     C     G     M readings  Y        C        G        M        L / cd/m2
  1    -4   -13   -17   -13      -2.48E-5  -8.53E-5  -1.30E-4  -1.05E-4   6.96E-6
 10    23    11    15    15       1.42E-4   7.21E-5   1.15E-4   1.22E-4   1.50E-4
 50   143    91    95   104       8.85E-4   5.97E-4   7.29E-4   8.43E-4   9.32E-4
 90   311   181   199   224       0.00192   0.00119   0.00153   0.00182   0.00204
 99   597   300   356   429       0.00369   0.00197   0.00273   0.00348   0.00398
100 16312 16305 16301 16307       0.101    0.107    0.125    0.132    0.0937
# flux from 0.528 sr ( 7.01E-7 sr/4px) is  5.62E-4 lx;
# tilewise luminance  9.99E-4 cd/m2 with rel. SD  106 % (summing pixels below 16380)
# dark frame dark/1m.pgm subtracted from all values
# Yell average= 166.3  minimum= -427  maximum=16312   over 16380: 129
# Cyan average=  98.2  minimum= -321  maximum=16305   over 16380: 170
# Gree average= 108.4  minimum= -512  maximum=16301   over 16380: 221
# Mage average= 121.7  minimum= -512  maximum=16307   over 16380: 121

End of results of "raw2lum" (version 1.22) with parameters:
  -c YCGM -fa -w 7.3 -fc1.03 -o 16380 -d dark/1m.pgm -sm200 -nh -i 39.txt -e 39.eps -n 39.ppm -t168 -c 3412 -s64 pgm/39.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)