Image 31

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 01:10:44
# Resolution   : 2048 x 1536 in jpeg (2064x1540 in pgm/31.pgm)
# Focal length : 23.4mm
# Exposure time: 0.001 s  (1/1000)
# Aperture     : f/4.0
# 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      -36.2    -38.4    -54.3    -52.4    -30.8  
 10   -22   -20   -26   -22      -21.0    -20.2    -30.7    -27.4    -18.0  
 50     0     0     0     0       0.00     0.00     0.00     0.00     0.00  
 90    20    20    24    22       19.0     20.2     28.3     27.4     16.3  
 99    38    38    44    40       36.2     38.4     52.0     49.9     31.5  
100  4334  3154  4418  2880       4.13E3   3.18E3   5.22E3   3.59E3   3.80E3
# flux from 0.0680 sr ( 8.61E-8 sr/4px) is -0.0110 lx;
# tilewise luminance -0.0106 cd/m2 with rel. SD-1.17E4 % (summing pixels below 16380)
# dark frame dark/off.pgm subtracted from all values
# Yell average=  -0.3  minimum=  -80  maximum= 4334   over 16380:   0
# Cyan average=  -0.2  minimum= -100  maximum= 3154   over 16380:   0
# Gree average=  -0.6  minimum= -102  maximum= 4418   over 16380:   0
# Mage average=  -0.4  minimum= -330  maximum= 2880   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 31.txt -e 31.eps -n 31.ppm -t168 -c 3412 -s64 pgm/31.pgm

Just points with luminances over 6.0E2 cd/m2. In grid tiles, flux densities from these points and tiles are given.
# Date/Time    : 2005:08:05 01:10:44
# Resolution   : 2048 x 1536 in jpeg (2064x1540 in pgm/31.pgm)
# Focal length : 23.4mm
# Exposure time: 0.001 s  (1/1000)
# Aperture     : f/4.0
# 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      -36.2    -38.4    -54.3    -52.4    -30.8  
 10   -22   -20   -26   -22      -21.0    -20.2    -30.7    -27.4    -18.0  
 50     0     0     0     0       0.00     0.00     0.00     0.00     0.00  
 90    20    20    24    22       19.0     20.2     28.3     27.4     16.3  
 99    38    38    44    40       36.2     38.4     52.0     49.9     31.5  
100  4334  3154  4418  2880       4.13E3   3.18E3   5.22E3   3.59E3   3.80E3
# flux from 2.74E-6 sr ( 8.61E-8 sr/4px) is  0.00388 lx;
# tilewise luminance  31.3 cd/m2 with rel. SD  695 % (points with luminances over  6.0E2 )
# dark frame dark/off.pgm subtracted from all values
# Yell average=1406.2  minimum=  -80  maximum= 4334   out of range: 794608
# Cyan average= 964.0  minimum= -100  maximum= 3154   out of range: 794608
# Gree average= 892.1  minimum= -102  maximum= 4418   out of range: 794608
# Mage average= 632.4  minimum= -330  maximum= 2880   out of range: 794608

End of results of "raw2lum" (version 1.22) with parameters:
  -c YCGM -ft -w 7.3 -fc1.03 -o 16380 -L600 -d dark/off.pgm -sm200 -nh -i 31.txt -e 31.eps -n 31.ppm -t168 -c 3412 -s64 pgm/31.pgm

Just points with luminances over 1.5 and below 50 cd/m2. In grid tiles, flux densities from these points and tiles are given.
# Date/Time    : 2005:08:05 01:10:44
# Resolution   : 2048 x 1536 in jpeg (2064x1540 in pgm/31.pgm)
# Focal length : 23.4mm
# Exposure time: 0.001 s  (1/1000)
# Aperture     : f/4.0
# 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      -36.2    -38.4    -54.3    -52.4    -30.8  
 10   -22   -20   -26   -22      -21.0    -20.2    -30.7    -27.4    -18.0  
 50     0     0     0     0       0.00     0.00     0.00     0.00     0.00  
 90    20    20    24    22       19.0     20.2     28.3     27.4     16.3  
 99    38    38    44    40       36.2     38.4     52.0     49.9     31.5  
100  4334  3154  4418  2880       4.13E3   3.18E3   5.22E3   3.59E3   3.80E3
# flux from 0.0310 sr ( 8.61E-8 sr/4px) is  0.523 lx;
# tilewise luminance  17.0 cd/m2 with rel. SD 3.57 % (points with luminances over  1.5    and below   50   )
# dark frame dark/off.pgm subtracted from all values
# Yell average=  12.0  minimum=  -80  maximum= 4334   out of range: 431634
# Cyan average=  -0.6  minimum= -100  maximum= 3154   out of range: 431634
# Gree average=  -5.8  minimum= -102  maximum= 4418   out of range: 431634
# Mage average=  -0.1  minimum= -330  maximum= 2880   out of range: 431634

End of results of "raw2lum" (version 1.22) with parameters:
  -c YCGM -ft -w 7.3 -fc1.03 -o 16380 -L1.5 -U50 -d dark/off.pgm -sm200 -nh -i 31.txt -e 31.eps -n 31.ppm -t168 -c 3412 -s64 pgm/31.pgm

Luminance scale / 1 
cd/m<sup>2</sup>
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)