[argyllcms] Re: Spec2CIE bug? Spectral values like 6.2125e+005, Lab values like 85.10/887.75/-759.54

  • From: Graeme Gill <graeme@xxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Wed, 15 Jun 2011 14:17:43 +1000

Alexey Gribunin wrote:
It seems to me that there is a bug in spec2cie v.1.3.3.

Hi,
        I don't actually regard it as a bug, although it is a bit
unusual. Basically the model says that there is some slight
emission from FWA at 420nm, and that due to the illuminant being
very small there (UV cut), the apparent reflectivity is
extremely high. But if you were then to multiply that reflectivity
by the UV cut illuminant, you will get a reasonable spectrum.

But in the highly artificial situation in which you then
take this apparent reflectance and multiply by some other
illuminant (like D50), then yes, you will get unexpected
CIE values. But think about the last - it doesn't make any
sense to do this since it doesn't correspond with any
real world situation. The actual sample only has an apparent
reflectance when illuminated by D50_0.0.sp. It won't
have that apparent reflectance if it were illuminated by D50.
So there is no physical situation corresponding with what
you are trying to do with the numbers. I.e. if you really
want the CIE values of a UV cut illumination, use the ones
produced by your second step. The third step is nonsense.

A way of eliminating this particular surprise however, is to correct D50_0.0.sp
so that it doesn't have any illumination that triggers FWA (which
was really the intention of it). See the attachment.

Graeme Gill.
SPECT

DESCRIPTOR "Argyll D50 illimunant spectral power, 0% U.V."

ORIGINATOR "Argyll CMS"

CREATED "Fri Jul 06 17:49:57 2001"
KEYWORD "SPECTRAL_BANDS"
SPECTRAL_BANDS "107"
KEYWORD "SPECTRAL_START_NM"
SPECTRAL_START_NM "300.000000"
KEYWORD "SPECTRAL_END_NM"
SPECTRAL_END_NM "830.000000"
KEYWORD "SPECTRAL_NORM"
SPECTRAL_NORM "100.000000"

KEYWORD "SPEC_300"
KEYWORD "SPEC_305"
KEYWORD "SPEC_310"
KEYWORD "SPEC_315"
KEYWORD "SPEC_320"
KEYWORD "SPEC_325"
KEYWORD "SPEC_330"
KEYWORD "SPEC_335"
KEYWORD "SPEC_340"
KEYWORD "SPEC_345"
KEYWORD "SPEC_350"
KEYWORD "SPEC_355"
KEYWORD "SPEC_360"
KEYWORD "SPEC_365"
KEYWORD "SPEC_370"
KEYWORD "SPEC_375"
KEYWORD "SPEC_380"
KEYWORD "SPEC_385"
KEYWORD "SPEC_390"
KEYWORD "SPEC_395"
KEYWORD "SPEC_400"
KEYWORD "SPEC_405"
KEYWORD "SPEC_410"
KEYWORD "SPEC_415"
KEYWORD "SPEC_420"
KEYWORD "SPEC_425"
KEYWORD "SPEC_430"
KEYWORD "SPEC_435"
KEYWORD "SPEC_440"
KEYWORD "SPEC_445"
KEYWORD "SPEC_450"
KEYWORD "SPEC_455"
KEYWORD "SPEC_460"
KEYWORD "SPEC_465"
KEYWORD "SPEC_470"
KEYWORD "SPEC_475"
KEYWORD "SPEC_480"
KEYWORD "SPEC_485"
KEYWORD "SPEC_490"
KEYWORD "SPEC_495"
KEYWORD "SPEC_500"
KEYWORD "SPEC_505"
KEYWORD "SPEC_510"
KEYWORD "SPEC_515"
KEYWORD "SPEC_520"
KEYWORD "SPEC_525"
KEYWORD "SPEC_530"
KEYWORD "SPEC_535"
KEYWORD "SPEC_540"
KEYWORD "SPEC_545"
KEYWORD "SPEC_550"
KEYWORD "SPEC_555"
KEYWORD "SPEC_560"
KEYWORD "SPEC_565"
KEYWORD "SPEC_570"
KEYWORD "SPEC_575"
KEYWORD "SPEC_580"
KEYWORD "SPEC_585"
KEYWORD "SPEC_590"
KEYWORD "SPEC_595"
KEYWORD "SPEC_600"
KEYWORD "SPEC_605"
KEYWORD "SPEC_610"
KEYWORD "SPEC_615"
KEYWORD "SPEC_620"
KEYWORD "SPEC_625"
KEYWORD "SPEC_630"
KEYWORD "SPEC_635"
KEYWORD "SPEC_640"
KEYWORD "SPEC_645"
KEYWORD "SPEC_650"
KEYWORD "SPEC_655"
KEYWORD "SPEC_660"
KEYWORD "SPEC_665"
KEYWORD "SPEC_670"
KEYWORD "SPEC_675"
KEYWORD "SPEC_680"
KEYWORD "SPEC_685"
KEYWORD "SPEC_690"
KEYWORD "SPEC_695"
KEYWORD "SPEC_700"
KEYWORD "SPEC_705"
KEYWORD "SPEC_710"
KEYWORD "SPEC_715"
KEYWORD "SPEC_720"
KEYWORD "SPEC_725"
KEYWORD "SPEC_730"
KEYWORD "SPEC_735"
KEYWORD "SPEC_740"
KEYWORD "SPEC_745"
KEYWORD "SPEC_750"
KEYWORD "SPEC_755"
KEYWORD "SPEC_760"
KEYWORD "SPEC_765"
KEYWORD "SPEC_770"
KEYWORD "SPEC_775"
KEYWORD "SPEC_780"
KEYWORD "SPEC_785"
KEYWORD "SPEC_790"
KEYWORD "SPEC_795"
KEYWORD "SPEC_800"
KEYWORD "SPEC_805"
KEYWORD "SPEC_810"
KEYWORD "SPEC_815"
KEYWORD "SPEC_820"
KEYWORD "SPEC_825"
KEYWORD "SPEC_830"
NUMBER_OF_FIELDS 107
BEGIN_DATA_FORMAT
SPEC_300 SPEC_305 SPEC_310 SPEC_315 SPEC_320 SPEC_325 SPEC_330 SPEC_335 
SPEC_340 SPEC_345 SPEC_350 SPEC_355 SPEC_360 SPEC_365 SPEC_370 SPEC_375 
SPEC_380 SPEC_385 SPEC_390 SPEC_395 SPEC_400 SPEC_405 SPEC_410 SPEC_415 
SPEC_420 SPEC_425 SPEC_430 SPEC_435 SPEC_440 SPEC_445 SPEC_450 SPEC_455 
SPEC_460 SPEC_465 SPEC_470 SPEC_475 SPEC_480 SPEC_485 SPEC_490 SPEC_495 
SPEC_500 SPEC_505 SPEC_510 SPEC_515 SPEC_520 SPEC_525 SPEC_530 SPEC_535 
SPEC_540 SPEC_545 SPEC_550 SPEC_555 SPEC_560 SPEC_565 SPEC_570 SPEC_575 
SPEC_580 SPEC_585 SPEC_590 SPEC_595 SPEC_600 SPEC_605 SPEC_610 SPEC_615 
SPEC_620 SPEC_625 SPEC_630 SPEC_635 SPEC_640 SPEC_645 SPEC_650 SPEC_655 
SPEC_660 SPEC_665 SPEC_670 SPEC_675 SPEC_680 SPEC_685 SPEC_690 SPEC_695 
SPEC_700 SPEC_705 SPEC_710 SPEC_715 SPEC_720 SPEC_725 SPEC_730 SPEC_735 
SPEC_740 SPEC_745 SPEC_750 SPEC_755 SPEC_760 SPEC_765 SPEC_770 SPEC_775 
SPEC_780 SPEC_785 SPEC_790 SPEC_795 SPEC_800 SPEC_805 SPEC_810 SPEC_815 
SPEC_820 SPEC_825 SPEC_830 
END_DATA_FORMAT

NUMBER_OF_SETS 1
BEGIN_DATA
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 
0.0 0.0 0.0 0.0 0.0 25.0 57.82 66.32 74.82 81.04 87.25 88.93 90.61 90.99 91.37 
93.24 95.11 93.54 91.96 93.84 95.72 96.17 96.61 96.87 97.13 99.61 102.1 101.43 
100.75 101.54 102.32 101.16 100.0 98.87 97.74 98.33 98.92 96.21 93.5 95.59 
97.69 98.48 99.27 99.16 99.04 97.38 95.72 97.29 98.86 97.26 95.67 96.93 98.19 
100.6 103.0 101.07 99.13 93.26 87.38 89.49 91.6 92.25 92.89 84.87 76.85 81.68 
86.51 89.55 92.58 85.4 78.23 67.96 57.69 70.31 82.92 80.6 78.27 78.91 79.55 
76.48 73.4 68.66 63.92 67.35 70.78 72.61 74.44
END_DATA

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