Image 11


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 00:35:45
# Resolution   : 2048 x 1536 in jpeg (2064x1540 in pgm/11.pgm)
# Focal length : 11.2mm
# Exposure time: 0.008 s  (1/125)
# Aperture     : f/2.8
# ISO equiv.   : 100

#c li count  min  Yav  max  ovf   min  Cav   max  ovf   min  Gav   max  ovf   min  Mav  max  ovf
# Image percentils         L=(1.000*1.30*Y+1.060*0.00*C+1.240*-0.30*G+1.310*0.00*M)* 0.0628
# %    Y     C     G     M readings  Y        C        G        M        L / cd/m2
  1   -38   -38   -46   -40      -2.4     -2.5     -3.6     -3.3     -2.0   
 10   -20   -20   -24   -22      -1.3     -1.3     -1.9     -1.8     -1.1   
 50     0     0     0     0       0.0      0.0      0.0      0.0      0.0   
 90    22    20    24    22       1.4      1.3      1.9      1.8      1.2   
 99    40    38    46    42       2.5      2.5      3.6      3.5      2.2   
100 16316 16322 16314 16314       1.0E3    1.1E3    1.3E3    1.3E3    9.5E2 
# flux from 5.55 sr ( 8.71E-6 sr/4px) is  0.466  (summing all pixels below 16380)
# dark frame dark/off.pgm has been subtracted from all values
# Yell average=   1.4  minimum=  -92  maximum=16316   over 16380:  18
# Cyan average=   0.5  minimum=  -78  maximum=16322   over 16380:  24
# Gree average=   0.3  minimum=  -94  maximum=16314   over 16380:  31
# Mage average=   0.8  minimum=  -98  maximum=16314   over 16380:  15

End of results of "raw2lum" (version 1.07) with parameters:
  -c YCGM -fa -w 7.3 -fc0.214 -o 16380 -d dark/off.pgm -sm200 -i 11.txt -e 11.eps -n 11.ppm -t156 -c 3412 -s32 pgm/11.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)