Hi Mauro,

The dE can be calculated from dL*, da* & db* as it is the square root of the sum of the squares odd L*, da* & db*. The formula below shows how.

Using $({L^*_1},{a^*_1},{b^*_1})$ and $({L^*_2},{a^*_2},{b^*_2})$ , two colors in L*a*b*:

$\Delta E_{ab}* = \sqrt{ (L^*_2-L^*_1)^2+(a^*_2-a^*_1)^2 + (b^*_2-b^*_1)^2 }$

I hope this helps you.

Best regards

Sean

Mr Sean Hillman

Business Manager

CERAM

Tel. +44 (0)1782 764321

-----Original Message-----
From: eci-en-bounces@lists.callassoftware.com [mailto:eci-en-bounces@lists.callassoftware.com] On Behalf Of Mauro Boscarol
Sent: 16 January 2011 13:32
To: Mailing List [ECI-EN]
Subject: [ECI-EN] Tolerance of proofing substrate color

I have a question about proofing ISO 12647-2:2007 (or Fogra 39).

The color of the print substrate used for proofing shall be in tolerance dE <= 3 with the color of the print substrate used for production (for example according to Media Wedge proofing process).

My question is: which document (and section) is this value of dE <= 3 specified?

12647-2 Table 1 specifies tolerance not in terms of dE but individually in terms of dL, da, db.

There is perhaps another document or another section?

Can you help me?

Thank you.

Mauro Boscarol

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