"white base: absolute" ?

darioluca

Well-known member
Hi there!

A client of ours sent us his color reading specs where you can also read: "white base: absolute" (see screenshot).
Schermata 2020-11-17 alle 08.10.36.jpg

Pity my English is not so skilled!
How do you interpret that?
The actual substrate must be white?
Or there must be a white backing under the measured sample?
Or what else?

Thanks to all!
 

cementary

Well-known member
That's part of measurement condition. White base can be relative to paper or absolute to white calibration plate. Strange to see it with deltaE. It actually matters if one measure density
 

darioluca

Well-known member
Thanks for your reply, but ... is there something else besides the "white calibration plate"? :oops:
I mean... all the spectros I've seen calibrate over their white calibration plate.
 

cementary

Well-known member
If you measure density between two patches on differently colored substrate resulting density value will include substrate density in it if you use absolute white base and will not if you use relative. That's why i don't see sense in including this parameter in deltaE measurement condition
 
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SteveSuffRIT

Well-known member
I think this means to measure over a white "backer".
Most paper is thin and translucent so opacity can be an issue.
Most prepress proofs are measured over white, while many press sheets are measured over black backer (because the color bar scanner has a black backer).
 

benstarr

Well-known member
I think this means to measure over a white "backer".
Most paper is thin and translucent so opacity can be an issue.
Most prepress proofs are measured over white, while many press sheets are measured over black backer (because the color bar scanner has a black backer).
This was my thought as well. I think it is referring to the backer.

Although perhaps the best way to get the answer is to go back to the client. You could say that you are assuming that means it is to be measured over a backing of the same color as the press sheet, but since you have not seen the specs worded this way in the past you would like to be certain.

This would also give you an opportunity to ask what "M" mode the color is referenced in. From the screenshot you provided it shows "filter" of none, which I would assume was M0, but with M1 being used very commonly now you might want to clarify that as well.
 

cementary

Well-known member
Come on, white base refers only to density measurements. No mistery, no speculation. And it just doesn't matter in terms of Lab values or deltaE measurements
 

Ulrich

Well-known member
Please be carefull to agree with delta E of <2!! I have never seen that realized!
not with DeltaE CIE 1976, but with the aclaimed DeltaE CIE 2000 it is possible
but not really simple in every case ,-)
 
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