Re: Silly question department, Display Media White Point
Re: Silly question department, Display Media White Point
- Subject: Re: Silly question department, Display Media White Point
- From: Steve Upton <email@hidden>
- Date: Thu, 19 Feb 2015 17:49:48 -0800
> On Feb 19, 2015, at 2:14 PM, Lars Borg <email@hidden> wrote:
>
> AdobeRGB ICC profile is in error, but too late to change it.
> Doug Walker explained it well to me why this is an error.
The way I get my head around it is this:
- the media wtpt tag should have values that are adapted to the white point of the PCS, which is D50
- in a print profile that was calculated relative to D50, the wtpt tag will have the same paper-white value as the D50 Lab value in the measurement set
- in a print profile that was calculated relative to another illuminant, like D65, the wtpt tag will not match the D65 Lab value in the measurement set. It will be the D65 white value adapted to D50.
- in a display profile the wtpt tag will contain the display’s wtpt value adapted to D50, which will *be* D50. So all v4 profiles contain D50 for the wtpt tag value. IF the display did not have D50 for its white point, then the chad tag will contain the adaptation matrix correspondingly.
When I asked about this in the past and expressed that I was dismayed that I could no longer look at the wtpt tag to determine the white point that a display was calibrated to, it was suggested that perhaps the view tag should contain this information. Alas, I have yet to see any software document the display’s white point in this tag….
regards,
Steve
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