Image 44


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 01:30:05
# Resolution   : 2048 x 1536 in jpeg (2064x1540 in pgm/44.pgm)
# Focal length : 13.8mm
# Exposure time: 4.000 s 
# Aperture     : f/3.0
# 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     8    -8   -16    -8       0.00107  -0.00114  -0.00266  -0.00140   0.00219
 10    52    20    20    28       0.00696   0.00284   0.00332   0.00491   0.00806
 50   576   252   276   368       0.0771   0.0358   0.0458   0.0646   0.0865
 90  3748  1536  1732  2464       0.502    0.218    0.288    0.432    0.566 
 99  9620  3980  4504  6404       1.29     0.565    0.748    1.12     1.45  
100 16348 16340 16336 16348       2.19     2.32     2.71     2.87     2.03  
# flux from 0.193 sr ( 2.48E-7 sr/4px) is  0.0394 lx;
# tilewise luminance  0.204 cd/m2 with rel. SD  124 % (summing pixels below 16380)
# dark frame dark/4s.pgm subtracted from all values
# Yell average=1371.0  minimum= -224  maximum=16348   over 16380: 244
# Cyan average= 578.5  minimum= -452  maximum=16340   over 16380: 305
# Gree average= 649.3  minimum= -512  maximum=16336   over 16380: 1506
# Mage average= 916.7  minimum= -512  maximum=16348   over 16380: 297

End of results of "raw2lum" (version 1.22) with parameters:
  -c YCGM -fa -w 7.3 -fc1.03 -o 16380 -d dark/4s.pgm -sm200 -nh -i 44.txt -e 44.eps -n 44.ppm -t168 -c 3412 -s64 pgm/44.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)