custom CMYK inks in Photoshop: set relative to D65 ?
custom CMYK inks in Photoshop: set relative to D65 ?
- Subject: custom CMYK inks in Photoshop: set relative to D65 ?
- From: email@hidden
- Date: Wed, 14 Dec 2005 15:27:34 -0600
Hi Danny,
Interesting observation! But notice that the Yxy -> Lab conversions are
dependent on what xy chromaticity is entered for Paper White (W). If it is
closer to D50 (.345, .358) the conversions are via D50 illuminant. If it
is closer to D65 chromaticity (.313, .329) the conversions are via D65
illuminant. There is a sudden transition somewhere about half way in
between.
Another Curious Quirk of Custom CMYK!
Mike Rodriguez
PreMedia Technologies
RR Donnelley
>
> -----Original Message-----
>
> Message: 15
> Date: Wed, 14 Dec 2005 14:12:03 -0500
> From: <email@hidden>
> Subject: custom CMYK inks in Photoshop: set relative to D65 ?
> To: email@hidden
> Message-ID: <email@hidden>
> Content-Type: text/plain; charset="ISO-8859-1"; format="flowed"
>
> To all,
>
> While making a check, I looked at the ink coordinates for
> SWOP coated in Photoshop. They can be shown in either xyY
> or L*a*b*, which is selected by a small checkbox in the
> dialog.
>
> I always assumed that, Photoshop always using the ICC PCS,
> and especially when selecting inks for CMYK profiles, this
> would be defined in D50. However, when converting from xyY
> to L*a*b* and vice-versa, my calculation match Photoshop
> only when I used D65, not D50.
>
> Is there a sort of default illuminant PS uses to handle
> these values? and which is automatically set set using my
> display profile or something else?
>
> I could not find any doc on this.
>
> Thanks,
>
> Danny Pascale
>
> email@hidden
> www.BabelColor.com
>
>
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