[argyllcms] Re: Question regarding White Point and spotread
- From: Brad Funkhouser <brad.funkhouser@xxxxxxxxxxx>
- To: "argyllcms@xxxxxxxxxxxxx" <argyllcms@xxxxxxxxxxxxx>
- Date: Tue, 04 Nov 2014 17:24:52 -0600
What's the black point tag Lab D50 value for that printer profile? It should
help explain the BPC shift. I think dark colors will shift up, slanting toward
that black point, and inward based on the shape of the bottom of the printer
gamut in relation to the shape of the bottom of the Beta gamut.
> On Nov 4, 2014, at 4:51 PM, <robert@xxxxxxxxxxxxxxxxxx> wrote:
>
> FYI Brad,
>
> Here is a new test with the Photoshop color setting to Absolute:
>
> Beta RGB: 20, 10, -11 6452, 1299, -1374 6452, 1299, -1374
> Absolute: 20, 10, -11 6460, 1308, -1374 6420, 1305, -1382
> Relative: 19, 10, -11 6235, 1300, -1348 6194, 1296, -1358
> Relative+BPC: 20, 9, -10 6615, 1182, -1332 6611, 1213, -1276
>
> The first row are the 8 and 16-bit Lab values in BetaRGB.
>
> The first set of 16-bit values are using Microsoft ICM, the second set Adobe
> ACE. The 8-bit values are the same for both CMMs.
>
> It's not possible to enter a color in 16-bit unfortunately.
>
> I'm a bit surprised to find the BPC altering the 'a' value so much (looking
> at the 16-bit values). ICM is worse than ACE here. I would have thought BPC
> would alter the 'L' value and not the 'a' and 'b' values.
>
> Robert
>
>
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