Which formula to calculate colour difference?

[fiatlux]

I'd like to use Bruce Lindbloom's online calculator the measure colour difference by entering L*a*b* values. But I'm not sure which method to use. His options and descriptions are:

CIE 1976 This is the standard CIE color difference method, which is simply the distance between the two colors, calculated in three-dimensional Lab color space.

CIE 1994 This is a more recent modification which has been recommended by CIE TC1-29 as the CIE94 color difference formula.

CIE 2000 This is a even more recent modification.

CMC (1:1) This method is drafted to become a new ISO standard (ISO 105-J03). This implementation uses a lightness weight of 1.0 and a chroma weight of 1.0 for use with perceptibility data.

CMC (2:1) As above, but using a lightness weight of 2.0 and a chroma weight of 1.0 for use with acceptability data.

(BTW for CMC I don't know what is meant by, or the significance of, "perceptibility data" vs "acceptability data.")

Thank you - FL

 

[Colorblind]

You can also go there:

http://printplanet.com/forums/color-management/19385-delta-e-equation-gracol-g7-proofing

 

[fiatlux]

So I should use CIE 1976?

FL

 

[cmcfarling]

If you are simply want to measure two colors and calculate the difference for your own personal use then can pick any formula really. Just be sure to use the same formula each time if you will be comparing more measurements in the future. If you are taking measurements to compare to a published spec like GRACoL then you need to use the formula that is used in the spec. In the case of GRACoL that is CIE 1976 (a.k.a. dE76, dEab). If you are comparing measurements to those from RIP software in which dE2000 was chosen as the color difference formula, then you would have to use dE2000 so that you are comparing apples to apples. The main thing is consistency. If you pass your numbers off to someone else make sure to include which formula you used.

If you're not sure, or you're not comparing to any documented spec then I would say choose the most common method which is dE76. In general when most people talk about delta E they are most likely referring to delta E calculated using the dE76 formula.

More info on delta E here
ColorWiki - Delta E: The Color Difference

 

[caveman]

I would like to add to the above that dE76 does not take into account the human eye perception of color, that is why you may not see any difference between two samples but calculate a high dE. Still, this is the formula to use for proofing purposes against any standard. For production purposes I would go with dE94 or 2000 which are more accurate to what we see. If I remeber correctly CMC formulas are targeted to the textile industry (may be wrong, please correct me if so).

 

[larrysison]

We still use dE76 when communicating color for both our press sheets and proofs. But I heard dE2000 may likely be the norm in the nearing future. dE2000 is already mentioned, though Informatively, in some ISO documentation.

Larry P. Sison
Ugra Certified Expert