Image 46


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 01:30:49
# Resolution   : 2048 x 1536 in jpeg (2064x1540 in pgm/46.pgm)
# Focal length : 13.8mm
# Exposure time: 0.017 s  (1/60)
# 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   -36   -38   -46   -40      -1.16    -1.29    -1.83    -1.68    -0.954 
 10   -18   -20   -24   -20      -0.579   -0.681   -0.957   -0.842   -0.465 
 50     6     2     2     4       0.193    0.0681   0.0797   0.168    0.227 
 90    30    24    28    28       0.964    0.818    1.12     1.18     0.919 
 99    60    44    52    52       1.93     1.50     2.07     2.19     1.89  
100 16326 16324 16322 16324        525      556      651      687      487  
# flux from 0.193 sr ( 2.48E-7 sr/4px) is  0.0493 lx;
# tilewise luminance  0.247 cd/m2 with rel. SD  133 % (summing pixels below 16380)
# dark frame dark/off.pgm subtracted from all values
# Yell average=   6.8  minimum=  -84  maximum=16326   over 16380:  20
# Cyan average=   2.2  minimum=  -92  maximum=16324   over 16380:  21
# Gree average=   2.2  minimum=  -98  maximum=16322   over 16380:  24
# Mage average=   3.9  minimum= -512  maximum=16324   over 16380:  19

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 46.txt -e 46.eps -n 46.ppm -t168 -c 3412 -s64 pgm/46.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)