[argyllcms] R: Re: Neutralize Grey Axis
- From: "realman10@xxxxxxxxx" <realman10@xxxxxxxxx>
- To: <argyllcms@xxxxxxxxxxxxx>
- Date: Wed, 12 Jan 2011 11:03:14 +0100 (CET)
Hi Klaus,
I'd like to ask you about the rationale for chosing the a,b values (-3,+11)
for the whitepoint as the opposite of the paper white (+3,-11).
I'm going to try the same but I was wondering about why you chose the opposite
to the paper white.
Thx
Michele
>----Messaggio originale----
>Da: lists@xxxxxxxxxxxxxxxxx
>Data: 11/01/2011 22.07
>A: <argyllcms@xxxxxxxxxxxxx>
>Ogg: [argyllcms] Re: Neutralize Grey Axis
>
>Nikolay Pokhilchenko wrote:
>> Tue, 11 Jan 2011 15:45:08 +0100 Klaus Karcher wrote:
>>
>>> You can calculate chromaticity coordinates
>>> for other adaptation colors using Bruce Lindbloom's Color Calculator
>>> <http://www.brucelindbloom.com/index.html?ColorCalculator.html> if
required.
>>>
>>> But as Gerhard mentioned and Graeme confirmed, changing the CIECAM
>>> adaptation chromaticity does not affect the gray balance of the
>>> perceptual intent essentially, so it might be better to replace it by
>>> -taa (Absolute appearance intent) as Graeme suggested. There's no gamut
>>> mapping in the absolute appearance intent however.
>>
>> I've just get the response from one photographer, my client: I've send him
new profile with customised viewing
>> conditions. He sad, that the BW prints isn't bluish now. The adaptation -
dpp -ds:n -dw:.345669:.358496 -da:100 -
>> df:.345669:.358496 is critical. It's not distinctive at a glance of simple
user, but is critical for pro photographers...
>> The ti3 from printer is attached in archieve.
>
>
>I've made some profiles with your ti3 file:
>
># "normal:"
>colprof -cmt -dpp -s sRGB.icc
>-D test_pap -O test_pap.icc 1931_FWA
>
># whitepoint D50
>colprof -cmt -dpp -dw:.345669:.358496 -s sRGB.icc
>-D test_D50 -O test_D50.icc 1931_FWA
>
># whitepoint + flare D50
>colprof -cmt -dpp -dw:.345669:.358496 -df:.345669:.358496 -s sRGB.icc
>-D test_D50f -O test_D50f.icc 1931_FWA
>
># whitepoint a = -3, b = +11
>colprof -cmt -dpp -dw:.367395:.393341 -s sRGB.icc
>-D test_-3+11 -O test_-3+11.icc 1931_FWA
>
># whitepoint + flare a = -3, b = +11
>colprof -cmt -dpp -dw:.367395:.393341 -df:.367395:.393341 -s sRGB.icc
>-D test_-3+11 -O test_-3+11.icc 1931_FWA
>
>icclu -fb -ip -s100 test_pap.icc
>50.000000 0.000000 0.000000 [Lab] -> Lut ->
>67.468898 65.014740 73.137592 [RGB]
>
>icclu -fb -ip -s100 test_D50.icc
>50.000000 0.000000 0.000000 [Lab] -> Lut ->
>67.222671 64.879958 70.825114 [RGB]
>
>icclu -fb -ip -s100 test_D50.icc
>50.000000 0.000000 0.000000 [Lab] -> Lut ->
>67.145810 64.781647 70.946942 [RGB]
>
>icclu -fb -ip -s100 test_-3+11.icc
>50.000000 0.000000 0.000000 [Lab] -> Lut ->
>67.957707 65.946592 67.968296 [RGB]
>
>icclu -fb -ip -s100 test_-3+11f.icc
>50.000000 0.000000 0.000000 [Lab] -> Lut ->
>67.682075 65.584257 68.362904 [RGB]
>
>icclu -ff -ia -s100 test_pap.icc
>
>100.00000 100.00000 100.00000 [RGB] -> Lut ->
>92.484190 3.264611 -11.250770 [Lab]
>
>67.468898 65.014740 73.137592 [RGB] -> Lut ->
>48.406617 2.075828 -7.193194 [Lab]
>
>67.222671 64.879958 70.825114 [RGB] -> Lut ->
>47.933146 1.290619 -4.797495 [Lab]
>
>67.145810 64.781647 70.946942 [RGB] -> Lut ->
>47.855776 1.367588 -5.066549 [Lab]
>
>67.957707 65.946592 67.968296 [RGB] -> Lut ->
>48.554256 0.018126 -0.290320 [Lab]
>
>67.682075 65.584257 68.362904 [RGB] -> Lut ->
>48.263415 0.242249 -1.194694 [Lab]
>
>∆E00 flat white -- paper white: 9.6
>∆E00 flat gray -- test_pap: 6.7
>∆E00 flat gray -- test_D50: 4.6
>∆E00 flat gray -- test_D50f: 4.9
>∆E00 flat gray -- test_-3+11: 0.3
>∆E00 flat gray -- test_-3+11f: 1.2
>
>icclu and xicclu -g confirm that the midtones in the D50 profiles are
>slightly less blue, but it needs further tweaking to make them
>completely neutral.
>
>Tweaking not only -dw but also -df makes little difference and has
>rather the opposite effect.
>
>In softproofs with test_-3+11, I percive the transition from neutral
>midtones to bluish highlights as annoying (more annoying than the
>overall blue cast in test_pap), but this might be a matter of taste.
>
>Klaus
>
>
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