Image 47


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 01:31:12
# Resolution   : 2048 x 1536 in jpeg (2064x1540 in pgm/47.pgm)
# Focal length : 13.8mm
# Exposure time: 0.004 s  (1/250)
# 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   -38   -38   -46   -42      -5.09    -5.39    -7.64    -7.37    -4.32  
 10   -20   -20   -26   -22      -2.68    -2.84    -4.32    -3.86    -2.19  
 50     0     0     0     0       0.00     0.00     0.00     0.00     0.00  
 90    22    20    24    22       2.95     2.84     3.99     3.86     2.63  
 99    38    38    46    42       5.09     5.39     7.64     7.37     4.32  
100 16304 11568 13662 11070       2.18E3   1.64E3   2.27E3   1.94E3   2.16E3
# flux from 0.193 sr ( 2.48E-7 sr/4px) is  0.0240 lx;
# tilewise luminance  0.120 cd/m2 with rel. SD  377 % (summing pixels below 16380)
# dark frame dark/off.pgm subtracted from all values
# Yell average=   0.7  minimum=  -92  maximum=16304   over 16380:   0
# Cyan average=   0.3  minimum=  -96  maximum=11568   over 16380:   0
# Gree average=  -0.0  minimum= -114  maximum=13662   over 16380:   2
# Mage average=   0.4  minimum= -512  maximum=11070   over 16380:   0

End of results of "raw2lum" (version 1.22) with parameters:
  -c YCGM -fa -w 7.3 -fc1.03 -o 16380 -d dark/off.pgm -sm200 -nh -i 47.txt -e 47.eps -n 47.ppm -t168 -c 3412 -s64 pgm/47.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)