Re: Finding CIELab Values from Target Chart TIF
Re: Finding CIELab Values from Target Chart TIF
- Subject: Re: Finding CIELab Values from Target Chart TIF
- From: Peter Skarpetis <email@hidden>
- Date: Thu, 29 Apr 2010 14:22:18 +1000
On 29/04/2010, at 1:57:32PM, Joseph Yates wrote:
> Peter
>
>> The Lab values you are seeing in photoshop are just a simulation. They are
>> calculated from the RGB / CMYK values in the tiff file using your current
>> colour settings. This is assuming that the TIFF file is not an Lab file.
>
> So the Lab values for the CMYK patches I'm getting in the Photoshop info
> palette are from my CMYK setting (ISOCoatedv2) even though when I open the
> CMYK Patch Chart (with no embedded profile) - I leave as is - and don't
> color manage?
>
>> If you wish to have more precision, use photoshop or any other image viewing
>> software to extract the RGB/CMYK values for the patches. You can then use
>> Colorsync utility or any other such tool to extract more precise Lab values
>> using CMYK/RGB profiles for the process you are trying to simulate.
>
> Can you describe this process in more detail? If I have the CMYK value of
> Patch 130 of 0/0/0/100% - how do I use ColorSync utility to get a more
> precise Lab value?
It is very simple really. Just launch the Colorsync utility, click on the calculator tab, put in a CMYK profile for the process you are trying to simulate, select Lab as the output and then type in some cmyk values.
Just remember that values are between 0 and 1, so for 50% you would enter 0.5, for 100.0 0.1 etc.
It is a bit of a manual process, but it should provide what you want.
Peter
>
>
> Joseph Yates | Pacifica Island Art | Maui, Hawaii
>
>
>
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