Christopher Edge recently mentioned that one method is to use multiple
sheets of the sample paper as the backing:
I have seen 3 definitions in ISO standards for backing: white, black, and
multiple sheets of the same paper stock.
Same-stock backing is generally my preference. To find out how many
sheets you need:
1) Start with a measurement of your paper sample on black backing.
2) Add an additional sheet of the sample paper under the first sheet.
3) Take another measurement and compare to the previous measurement.
4) Repeat steps 2 & 3 until there is no significant color change.
I don't think I've ever needed more than 5-6 sheets of backing material.
-jeff
Roger Breton wrote:
Date: Wed, 12 Jul 2006 23:11:49 -0400
From: Roger Breton
Subject: Re: ISO 12647-3 measurement (IT8.74 or ECI 2002) Lab data
list---black backing and white backing
To: "Edge, Christopher", ColorSync
<email@hidden>
Content-Type: text/plain; charset=ISO-8859-1
> I have seen 3 definitions in ISO standards for backing: white, black, and
> multiple sheets of the same paper stock. If the paper stock is identical
> between two systems you are trying to match, there should be no problem
> using any of the above. If you are doing absolute rendering for proofing on
> different paper stocks or performing virtual proofing on a display, then you
> will observe significant differences of appearance, particularly between
> very thin and very thick paper stocks.
How, then, could you compare thin paper stocks among themselves, on color?
If measured on a black backing, they could appear (some #5 coated grades I
know) very neutral, with a* and b* close to zero. On the other hand, if
measured on a white backing, like the Spectroscan table, the same paper
shows a negative b* value, typically around -3, again for some papers I'm
familiar with. As a consequence, I can hardly tell unequivocally what is the
"color" of a thin paper stock. Lately, before loosing my mental sanity, I
started measuring over "nothing": I place the paper one inch away off the
surface of my desk so there is no backing behind it, just the space between
the top of my desk and the floor, about 30" or so. Then I measure, with my
SpectroEye, holding the paper from underneath between my fingers. It works.
But it's not an ISO standard :(