Hi, in 2010 Fogra did a research project where several colour difference formulas were tested for different applications. Here applications does not mean different coloration-processes but different aims when choosing a colour difference formula. If the aim is modelling the judgment of a human observer in terms of how big a colour difference is perceived, dE2000 performed best for printed samples in this research. Some details (also the data set that was used) can be found online: http://www.fogra.org/en/fogra-research/prepress/completed/colour-difference-metrics/a-colour-difference-metrics.html Best regards Claas Am 20.07.2012 um 16:50 schrieb Jason Campbell: > Hi there. Sorry for jumping in but I generally lurk on the list but liked > this discussion... > > dE76 is a generally accepted Delta-E computation for color difference. As > Lab is a three dimensional space, dE76 is a simple Euclidean distance between > the two three dimensional points (your two Lab values). For the most part, > it gives a good sense of how far you are off in terms of color difference. > It is also nice since it is super easy to calculate. > > The other varieties of Delta-E all attempt to improve on the simplistic > approach of dE76 by better modeling human color perception. The most recent, > dE2000 is a very convoluted set of equations. As you have already noted > Lindbloom's excellent website, you will have no doubt taken a look at this > monstrosity. However, it does do a lot to blend many of the nuances of color > perception into the calculation. > > In the end, there is no "right one" or even "best one" as each dE function > can be considered well-tailored to certain applications. For example, dE-CMC > is often used in textiles. For graphic arts, dE76 is still generally > considered the 'standard' if you will. It continues to be the dE used in > such things as the G7 GRACoL specification. A colleague of mine participates > in a number of print industry standards committees and has indicated that > there has been a lot of talk about moving toward dE2000 as the new > specification. But that is talk, still not the de facto. > > > > On Fri, Jul 20, 2012 at 10:06 AM, Stephen T <stwebvanuatu@xxxxxxxxxxxx> wrote: > Here are some examples. The input data is a direct cut-and-paste from the > colprof output. I have calculated delta E with Gaurav Sharma's spreadsheet > and Bruce Lindblooms web calculator: > > http://www.ece.rochester.edu/~gsharma/ciede2000/ > http://www.brucelindbloom.com/index.html?Eqn_DeltaE_CIE2000.html > > [5.790875] 0.018533 0.060767 0.188920 -> 16.184140 24.186926 -63.268069 > should be 19.349371 22.206153 -58.841773 > DE00 spreadsheet = 2.4096 > DE00 Lindbloom = 2.4096 > DE76 Lindbloom = 5.7909 > [1.906550] 0.863110 0.849700 0.848230 -> 94.689681 -0.383334 0.713823 should > be 96.521931 -0.897156 0.596434 > DE00 spreadsheet = 1.3233 > DE00 Lindbloom = 1.3233 > DE76 Lindbloom = 1.9066 > [3.648782] 0.114370 0.224380 0.096200 -> 54.928708 -42.874429 37.209866 > should be 52.027751 -44.149537 39.018775 > DE00 spreadsheet = 2.8834 > DE00 Lindbloom = 2.883450 > DE76 Lindbloom = 3.648781 > [4.530066] 0.286760 0.036334 0.022012 -> 38.996835 61.855796 36.960859 should > be 36.036227 64.919159 38.501022 > DE00 spreadsheet = 2.6417 > DE00 Lindbloom = 2.6417 > DE76 Lindbloom = 3.063 > [5.273161] 0.651050 0.422930 0.106950 -> 79.796759 4.157840 84.383180 should > be 80.569480 3.851387 89.590407 > DE00 spreadsheet = 1.2209 > DE00 Lindbloom = 1.2209 > DE76 Lindbloom = 5.2732 > [3.185483] 0.357800 0.131360 0.220400 -> 48.673987 54.123752 -12.755375 > should be 48.059068 55.331845 -15.638028 > DE00 spreadsheet = 1.3801 > DE00 Lindbloom = 1.3801 > DE76 Lindbloom = 3.1855 > [3.829559] 0.071679 0.252420 0.368150 -> 49.812685 -30.674000 -32.260727 > should be 47.791690 -33.193813 -30.203630 > DE00 spreadsheet = 2.5854 > DE00 Lindbloom = 2.5854 > DE76 Lindbloom = 3.8296 > [2.015927] 0.023399 0.024048 0.024181 -> 17.588819 -0.942403 -0.176957 should > be 15.938875 -0.417952 -1.209720 > DE00 spreadsheet = 1.6780 > DE00 Lindbloom = 1.6780 > DE76 Lindbloom = 2.0159 > [11.990115] 0.407720 0.321030 0.050649 -> 70.288554 -10.231232 101.435263 > should be 72.415918 -9.806180 89.643040 > DE00 spreadsheet = 2.7719 > DE00 Lindbloom = 2.7719 > DE76 Lindbloom = 11.9901 > > I must have not noticed before that the delta E reported by colprof (flag -y) > exactly matches DE76. Anyone can easily verify this with their own data and > calculation of delta E for just one patch will do. Graeme has also confirmed > that colprof returns DE76 (Euclidean distance). > > The next question's are: > > Is DE76 used only for reporting errors or is it used in colprof for model > fitting as well? > > Which delta E function is most appropriate for profiling (my application is > graphic arts)? Note there's a huge difference between DE76 = 11.99 and DE00 = > 2.77 for the last patch in the above examples. > > Stephen. > > From: Graeme Gill <graeme@xxxxxxxxxxxxx> > To: argyllcms@xxxxxxxxxxxxx > Sent: Thursday, 19 July 2012 11:53 PM > Subject: [argyllcms] Re: How is delta E calculated in colprof? > > Stephen T wrote: > > Both of the above are consistent but colprof's delta E values are different > > and do not match > > DE76 and DE94 either. > > Hi, > do you have a specific example ? > > > Which delta E is colprof reporting? The documentation states only that "a > > summary of the average > > and maximum Lab delta E's will be printed out if this flag [-y] is set". > > There is no qualification, so this is plain delta E (ie. Euclidean distance). > It's > open source, so you can always look at the source code... > > > Is colprof applying any weighting to the DE00 calculation: KL, KC, KH not > > equal to 1.0? > > Again, it's open source - it's easy enough to check, and it's noted in the > source that the equations are taken from: > > "The CIEDE2000 Color-Difference Formula: Implementation Notes, > Supplementary Test Data, and Mathematical Observations", by > Gaurav Sharma, Wencheng Wu and Edul N. Dalal, > Color Res. Appl., vol. 30, no. 1, pp. 21-30, Feb. 2005. > > Graeme Gill. > > > >