Fwd: CGATS text file from a profile
Fwd: CGATS text file from a profile
- Subject: Fwd: CGATS text file from a profile
- From: Eric Nunn <email@hidden>
- Date: Fri, 18 Mar 2011 15:37:05 +0000
Thanks for replying Steve.
What I am basically asking is, say a newspaper printer who is using ISONewspaper26v4 as his standard profile, needs to print a supplement on pink paper, like the Financial Times. Could you edit the whitepoint of the standard profile to reflect the new Lab values and by converting source RGB files using absolute rendering, end up with a set of separations that are tailored to that new target condition adapting the greybalance etc to maintain colour appearance as far as possible?
Many thanks
Eric
> On 17 Mar 2011, at 19:34, Steve Upton wrote:
>
>> At 9:25 AM +0000 3/17/11, Eric Nunn wrote:
>>> I'd like to ask a supplemental question on this if I may.
>>> If I take the ISO newsprint profile - ISONewspaper26v4 - edit the whitepoint tag to reflect a Financial Times type paper colour, e.g. L81. a12. b22, I can "inject" the effect of that substrate across the whole colourspace but only if I use absolute rendering?
>>
>> correct.
>>
>>> So when converting from RGB if I use relative colorimetric the edit I have made makes no difference, but if I do an absolute colorimetric conversion, I can in effect "subtract" the paper colour from the colourspace.
>>
>> ... not sure what you mean here...
>>
>>> Have I understood this correctly?
>>
>> I don't think so. The white point edit is useful when the profile is used for proofing (the CMYK->Lab transform is in use). I don't think it has an effect on the rendering of the profile at all, though I could be wrong.
>>
>> Are you thinking that you would like to improve the output of a profile if you adjust the profile's white point to match your paper white?
>>
>> Honestly, I'm not sure. It might make a difference for abs col output but that's pretty rare in CMYK output. You often end up with D65 blue-white as the image's white which can be pretty nasty. Photoshop CS5 now overrides that white point for D65 working spaces though I haven't looked into what's really going on there.
>>
>> For spot/custom colors though, it might make a difference...
>>
>> worth a try
>>
>> regards,
>>
>> Steve
>>
>>
>> ________________________________________________________________________
>> o Steve Upton CHROMiX www.chromix.com
>> o (hueman) 866.CHROMiX
>> o email@hidden 206.985.6837
>>
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