Colour Management: Matching two Gretag Macbeth Color Checkers

D
Posted By
Dinarius
Nov 30, 2006
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431
Replies
3
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Closed
I have downloaded a complete set of Gretag Macbeth Colour Checker files from here>

< http://www.babelcolor.com/main_level/ColorChecker.htm#How_ab out_data>

Click on ‘How About Images’ from the list of topics just below the top of the page.

Then click on ‘ALL images "from AVG"’and download the set of files.

I am using the Adobe 1998 16bit file.

Firstly, I shoot a Gretag CC under even lighting. Using Adjust in ACR and then Curves and H/S layers in CS2, I correct the 16 bit file in Adobe 1998 so that all the grey scale patches on the bottom row, as well as the Red, Green, Blue and Yellow patches are exactly as they should be. e.g. Red is 152, 52, 59. White is 245, 245, 240. etc…etc….

My problem is this: when I open both the Bablecolor ‘master’ Gretag CC file and my corrected Gretag CC file together on my screen, they don’t look the same. My color patches are a bit more saturated. I realize that I am only correcting 10 of 24 patches, but I would expect the 4 colour patches to look the same.

If I hold the Color Sampler Tool over the R,G,B,Y patches on both charts, the readings are identical.

So, why don’t they look the same?

What can I adjust, if anything, to make them look the same without messing up my corrections?

Many thanks.

D.

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JL
Joel_L.
Nov 30, 2006
Sorry that I can’t answer your question, but it sounds like the type of specialized question that they would love over in the Adobe Color Management Forum:

http://www.adobeforums.com/cgi-bin/webx?14@@.eea5b31
CC
Chris_Cox
Nov 30, 2006
Gretag MacBeth’s published values are wrong to start with. So, don’t trust the images based on GM data. Their averaged images are more likely to be accurate.

Plus, different cameras are going to have slightly different metamerism problems (because of slightly different color filters). That’s unavoidable, I’m afraid.

Now, how far off are those other color squares?
D
Dinarius
Dec 1, 2006
Joel,

Thanks for the tip. I will post it there too.

Chris,

Yes, I am aware that Gretag’s values are wrong. That’s why I use Babelcolor’s, which are highly regarded. Also, I use their averaged values, which are better still.

As to how far off they are…….they’re not very, but still……! 😉

Thanks.

D.

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