Image 41


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 01:22:12
# Resolution   : 2048 x 1536 in jpeg (2064x1540 in pgm/41.pgm)
# Focal length :  8.2mm
# Exposure time: 0.250 s  (1/4)
# Aperture     : f/2.5
# 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      -0.0565  -0.0599  -0.0849  -0.0819  -0.0480
 10   -20   -20   -24   -22      -0.0298  -0.0315  -0.0443  -0.0429  -0.0254
 50     0     0     0     0       0.00     0.00     0.00     0.00     0.00  
 90    22    22    26    24       0.0327   0.0347   0.0480   0.0468   0.0282
 99    40    40    48    44       0.0595   0.0631   0.0886   0.0858   0.0508
100 16318 16304 16314 16318       24.3     25.7     30.1     31.8     22.5  
# flux from 0.528 sr ( 7.01E-7 sr/4px) is  6.32E-4 lx;
# tilewise luminance  7.40E-4 cd/m2 with rel. SD  587 % (summing pixels below 16380)
# dark frame dark/off.pgm subtracted from all values
# Yell average=   0.9  minimum= -100  maximum=16318   over 16380:  14
# Cyan average=   0.4  minimum=  -84  maximum=16304   over 16380:  11
# Gree average=   0.8  minimum=  -98  maximum=16314   over 16380:  15
# Mage average=   0.8  minimum=  -88  maximum=16318   over 16380:   7

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 41.txt -e 41.eps -n 41.ppm -t168 -c 3412 -s64 pgm/41.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)