Re: Conversion of RGB values to LAB values
Re: Conversion of RGB values to LAB values
- Subject: Re: Conversion of RGB values to LAB values
- From: Lorenzo Ridolfi <email@hidden>
- Date: Thu, 20 Jan 2005 15:11:54 -0200
I would like to convert RGB values (adobe98) to CIE LAB values. Given
that I would like to convert 918 of them from a test chart, I would prefer
to do this in a spreadsheet or executable rather than using the dropper
tool in photoshop and typing 2754 number sets. Anybody have a nice tool
for doing this?
Tim,
You may use Colorlab from Gretag (free) at
http://www.gretagmacbeth.com/index/products/products_color-mgmt-spec/products_professional-cm/products_pm5-photostudio/products_pm5-photostudio_sw.htm
The procedure I use (from Real World Color Management) is a little bit complex:
1) open the testchart in Colorlab,
2) convert it to a image with each patch with 1x1 pixel,
3) save as tiff image
3) go to photoshop, convert it to lab values using the right profile (in
your case AdobeRGB)
4) Open the tiff image with lab values in Colorlab
5) Change the filter mode to Lab
6) Convert the image to spot colors
7) Save (finally) the Lab values as textfile.
This long procedure is need when your workflow use Photoshop CMM and you
want to have the same colorspace convertion in you data files. Colorlab has
some CMM options (that could made this procedure simpler) but I use the
Photoshop CMM.
This procedure is useful for printer profies, if you want to convert the
colors only in "well behaved" colorspaces, like AdobeRGB, it's not
difficult to write a program or a excel. You can get the math in
www.brucelindbloom.com.
Regards,
Lorenzo
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