3b. About the Charts: ColorChecker DC


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Chart Description

ColorChecker DC Chart

The ColorChecker DC chart has a large white patch in the center, immediately surrounded by a set of various neutral gray patches. These are used for global color balance and tone reproduction purposes. The center patch is very helpful to the photographer in determining the proper exposure of the chart (a topic that will be discussed in the next chapter).

The patches around the outer edge of the chart allow you to judge the uniformity of illumination of the chart (a topic that is discussed further here). If you see that the lighting is not even across the chart, you are advised to correct this problem before proceeding to make the profile.

Colors S4 through S11 have a glossy surface finish, and because of that, they can represent more extreme colors which extend the "knowable" color range of the profile. However, many photographers feel that this gloss can pick up unwanted reflections, thereby polluting the color of the patch, resulting in an inferior profile. Other photographers are comfortable setting up the shot in such a way as to avoid these reflections. Since there is no consensus on this matter, inCamera may instructed to either include or exclude the glossy colors when the profile is made.


Reference File

ColorChecker DC charts are available in two forms: batch measured and custom measured. In either case, a reference file for the chart is provided with the chart. Use this file with inCamera. Your reference file may or may not contain spectral data. Older reference files did not, but GretagMacbeth (the manufacturer of the ColorChecker DC chart) has recently made spectral reference files available. inCamera will work with either kind of reference file, but you can specify your light source only when using spectral reference files. The inCamera installation package includes a spectral reference file from GretagMacbeth named ColorChecker DC.txt.


Power Users Only: Custom Data Reference Files

If you wish to make a custom reference file, it must be in one of the two following formats.

The beginning and ending of ColorChecker DC.txt (an example of the spectral format) is shown here:

LGOROWLENGTH	12
CREATED	"12/15/2003"  # Time: 15:08
INSTRUMENTATION	"SpectroScanT"
MEASUREMENT_SOURCE	"Illumination=D50	ObserverAngle=2°	WhiteBase=Abs	Filter=No"
ILLUMINATION_NAME	"D50"
OBSERVER_ANGLE	"2"
KEYWORD	"SampleID"
KEYWORD	"SAMPLE_NAME"
NUMBER_OF_FIELDS	38
BEGIN_DATA_FORMAT
SampleID	SAMPLE_NAME	nm380	nm390	nm400	nm410	nm420	nm430	nm440	nm450	nm460	nm470	nm480	nm490	nm500	nm510	nm520	nm530	nm540	nm550	nm560	nm570	nm580	nm590	nm600	nm610	nm620	nm630	nm640	nm650	nm660	nm670	nm680	nm690	nm700	nm710	nm720	nm730
END_DATA_FORMAT
NUMBER_OF_SETS	240
BEGIN_DATA
1	A1	0.1406	0.1994	0.3760	0.6298	0.7718	0.8014	0.8049	0.8056	0.8058	0.8039	0.8021	0.8011	0.7984	0.7961	0.7957	0.7937	0.7925	0.7899	0.7856	0.7857	0.7821	0.7787	0.7741	0.7693	0.7663	0.7628	0.7625	0.7644	0.7663	0.7653	0.7644	0.7647	0.7645	0.7659	0.7697	0.7755
2	A2	0.0312	0.0347	0.0339	0.0344	0.0343	0.0342	0.0344	0.0340	0.0335	0.0334	0.0330	0.0329	0.0325	0.0322	0.0321	0.0317	0.0317	0.0314	0.0310	0.0309	0.0304	0.0302	0.0298	0.0297	0.0296	0.0295	0.0297	0.0297	0.0301	0.0301	0.0304	0.0304	0.0303	0.0309	0.0311	0.0316
3	A3	0.0903	0.1232	0.1674	0.1900	0.1937	0.1984	0.2021	0.2036	0.2036	0.2016	0.2005	0.2000	0.1994	0.1998	0.2005	0.2006	0.2008	0.1998	0.1987	0.1987	0.1978	0.1967	0.1943	0.1919	0.1895	0.1870	0.1857	0.1842	0.1833	0.1814	0.1793	0.1771	0.1753	0.1753	0.1758	0.1773
4	A4	0.1383	0.2016	0.3787	0.6342	0.7773	0.8066	0.8101	0.8111	0.8105	0.8088	0.8067	0.8056	0.8028	0.8005	0.8001	0.7982	0.7969	0.7945	0.7903	0.7906	0.7870	0.7835	0.7786	0.7734	0.7704	0.7666	0.7667	0.7681	0.7697	0.7687	0.7679	0.7677	0.7676	0.7684	0.7721	0.7779
5	A5	0.0313	0.0342	0.0340	0.0342	0.0342	0.0341	0.0342	0.0339	0.0335	0.0336	0.0331	0.0329	0.0326	0.0323	0.0321	0.0319	0.0318	0.0314	0.0311	0.0309	0.0303	0.0300	0.0297	0.0295	0.0296	0.0296	0.0298	0.0300	0.0302	0.0304	0.0306	0.0306	0.0308	0.0310	0.0311	0.0317
6	A6	0.0898	0.1256	0.1694	0.1908	0.1958	0.1996	0.2034	0.2050	0.2047	0.2031	0.2017	0.2012	0.2008	0.2009	0.2015	0.2016	0.2016	0.2008	0.1995	0.1997	0.1987	0.1973	0.1951	0.1924	0.1900	0.1874	0.1860	0.1848	0.1835	0.1817	0.1798	0.1774	0.1759	0.1755	0.1765	0.1774
7	A7	0.1428	0.2073	0.3863	0.6390	0.7783	0.8072	0.8105	0.8121	0.8114	0.8100	0.8081	0.8071	0.8041	0.8021	0.8015	0.7999	0.7987	0.7962	0.7918	0.7919	0.7887	0.7851	0.7803	0.7752	0.7720	0.7683	0.7680	0.7695	0.7714	0.7700	0.7692	0.7690	0.7691	0.7698	0.7731	0.7793
8	A8	0.0312	0.0338	0.0342	0.0347	0.0346	0.0347	0.0344	0.0343	0.0341	0.0337	0.0335	0.0333	0.0329	0.0327	0.0325	0.0322	0.0320	0.0317	0.0314	0.0312	0.0308	0.0305	0.0301	0.0300	0.0301	0.0301	0.0302	0.0303	0.0306	0.0309	0.0310	0.0309	0.0309	0.0314	0.0316	0.0311
9	A9	0.0879	0.1256	0.1684	0.1901	0.1957	0.1994	0.2030	0.2055	0.2047	0.2032	0.2020	0.2014	0.2012	0.2013	0.2021	0.2024	0.2022	0.2017	0.2004	0.2004	0.1996	0.1980	0.1962	0.1935	0.1912	0.1890	0.1873	0.1864	0.1851	0.1832	0.1812	0.1790	0.1775	0.1771	0.1777	0.1791
10	A10	0.1354	0.1959	0.3716	0.6268	0.7736	0.8048	0.8090	0.8100	0.8096	0.8078	0.8062	0.8049	0.8022	0.7999	0.7993	0.7976	0.7966	0.7939	0.7897	0.7895	0.7863	0.7827	0.7780	0.7731	0.7698	0.7664	0.7665	0.7680	0.7698	0.7689	0.7674	0.7678	0.7679	0.7689	0.7734	0.7799
11	A11	0.0353	0.0320	0.0347	0.0343	0.0341	0.0344	0.0342	0.0339	0.0335	0.0335	0.0331	0.0331	0.0325	0.0323	0.0323	0.0320	0.0318	0.0315	0.0310	0.0310	0.0305	0.0302	0.0299	0.0297	0.0298	0.0297	0.0298	0.0301	0.0303	0.0306	0.0305	0.0306	0.0307	0.0310	0.0315	0.0312
12	A12	0.0901	0.1242	0.1667	0.1886	0.1940	0.1974	0.2014	0.2031	0.2025	0.2013	0.2000	0.1994	0.1991	0.1991	0.1999	0.2000	0.2000	0.1993	0.1981	0.1980	0.1972	0.1955	0.1935	0.1911	0.1887	0.1863	0.1847	0.1837	0.1825	0.1806	0.1785	0.1762	0.1749	0.1748	0.1751	0.1763
13	B1	0.0898	0.1243	0.1665	0.1889	0.1937	0.1978	0.2015	0.2037	0.2030	0.2016	0.2005	0.1999	0.1997	0.1999	0.2006	0.2009	0.2009	0.2002	0.1989	0.1992	0.1980	0.1966	0.1945	0.1919	0.1896	0.1872	0.1858	0.1845	0.1835	0.1817	0.1795	0.1774	0.1758	0.1758	0.1764	0.1771
14	B2	0.0479	0.0472	0.0461	0.0449	0.0443	0.0440	0.0434	0.0431	0.0422	0.0414	0.0407	0.0401	0.0396	0.0394	0.0394	0.0396	0.0401	0.0411	0.0428	0.0467	0.0538	0.0659	0.0922	0.1423	0.1925	0.2244	0.2425	0.2535	0.2605	0.2650	0.2690	0.2740	0.2804	0.2872	0.2936	0.2998
...
227	S11	0.0462	0.0722	0.1166	0.1527	0.1681	0.1895	0.2217	0.2611	0.3035	0.3575	0.3910	0.3916	0.3599	0.3069	0.2448	0.1849	0.1361	0.0977	0.0691	0.0516	0.0418	0.0359	0.0317	0.0286	0.0269	0.0258	0.0255	0.0256	0.0264	0.0268	0.0260	0.0250	0.0239	0.0237	0.0256	0.0291
228	S12	0.0887	0.1230	0.1669	0.1891	0.1944	0.1987	0.2021	0.2040	0.2033	0.2021	0.2009	0.2000	0.1999	0.2000	0.2008	0.2009	0.2009	0.2001	0.1987	0.1989	0.1978	0.1965	0.1943	0.1918	0.1894	0.1870	0.1855	0.1844	0.1831	0.1815	0.1792	0.1770	0.1757	0.1752	0.1759	0.1769
229	T1	0.0915	0.1247	0.1685	0.1901	0.1951	0.1993	0.2031	0.2051	0.2046	0.2029	0.2017	0.2010	0.2008	0.2010	0.2017	0.2018	0.2017	0.2010	0.1997	0.1997	0.1987	0.1972	0.1950	0.1927	0.1903	0.1879	0.1865	0.1856	0.1845	0.1827	0.1806	0.1786	0.1771	0.1770	0.1774	0.1790
230	T2	0.0341	0.0342	0.0349	0.0354	0.0353	0.0353	0.0351	0.0350	0.0346	0.0344	0.0342	0.0338	0.0337	0.0333	0.0332	0.0330	0.0328	0.0326	0.0321	0.0319	0.0315	0.0312	0.0309	0.0307	0.0308	0.0307	0.0307	0.0310	0.0313	0.0315	0.0314	0.0316	0.0318	0.0318	0.0323	0.0324
231	T3	0.1387	0.1983	0.3765	0.6319	0.7749	0.8055	0.8086	0.8093	0.8091	0.8073	0.8054	0.8045	0.8018	0.7996	0.7993	0.7975	0.7963	0.7940	0.7896	0.7900	0.7868	0.7834	0.7787	0.7740	0.7710	0.7674	0.7675	0.7690	0.7708	0.7698	0.7685	0.7686	0.7684	0.7699	0.7728	0.7798
232	T4	0.0874	0.1217	0.1663	0.1883	0.1932	0.1974	0.2009	0.2031	0.2026	0.2011	0.1998	0.1992	0.1991	0.1991	0.2000	0.2000	0.2002	0.1995	0.1983	0.1984	0.1975	0.1961	0.1939	0.1914	0.1890	0.1867	0.1852	0.1842	0.1829	0.1812	0.1789	0.1768	0.1752	0.1750	0.1756	0.1768
233	T5	0.0316	0.0324	0.0337	0.0339	0.0333	0.0339	0.0336	0.0334	0.0333	0.0331	0.0330	0.0325	0.0323	0.0320	0.0319	0.0316	0.0314	0.0312	0.0307	0.0306	0.0302	0.0298	0.0295	0.0294	0.0295	0.0294	0.0294	0.0297	0.0300	0.0302	0.0303	0.0303	0.0306	0.0306	0.0305	0.0307
234	T6	0.1401	0.1988	0.3761	0.6303	0.7736	0.8040	0.8074	0.8085	0.8079	0.8065	0.8046	0.8039	0.8011	0.7986	0.7981	0.7964	0.7953	0.7929	0.7884	0.7889	0.7855	0.7819	0.7771	0.7723	0.7692	0.7655	0.7653	0.7669	0.7686	0.7675	0.7665	0.7666	0.7665	0.7676	0.7709	0.7781
235	T7	0.0888	0.1224	0.1669	0.1883	0.1936	0.1978	0.2014	0.2035	0.2029	0.2016	0.2002	0.1997	0.1994	0.1997	0.2004	0.2007	0.2007	0.2000	0.1986	0.1989	0.1979	0.1966	0.1946	0.1921	0.1898	0.1873	0.1859	0.1849	0.1835	0.1818	0.1796	0.1774	0.1758	0.1756	0.1765	0.1773
236	T8	0.0310	0.0334	0.0334	0.0333	0.0331	0.0332	0.0331	0.0328	0.0326	0.0326	0.0324	0.0319	0.0318	0.0315	0.0313	0.0311	0.0309	0.0306	0.0303	0.0302	0.0297	0.0294	0.0291	0.0290	0.0290	0.0289	0.0289	0.0293	0.0295	0.0298	0.0296	0.0299	0.0300	0.0299	0.0305	0.0302
237	T9	0.1352	0.1973	0.3741	0.6292	0.7720	0.8021	0.8057	0.8065	0.8068	0.8054	0.8034	0.8030	0.8004	0.7983	0.7980	0.7963	0.7952	0.7927	0.7883	0.7888	0.7854	0.7818	0.7775	0.7728	0.7698	0.7663	0.7663	0.7680	0.7699	0.7687	0.7677	0.7678	0.7678	0.7688	0.7719	0.7785
238	T10	0.0890	0.1239	0.1684	0.1894	0.1949	0.1991	0.2026	0.2046	0.2038	0.2027	0.2014	0.2009	0.2006	0.2008	0.2015	0.2017	0.2017	0.2010	0.1998	0.1999	0.1988	0.1975	0.1954	0.1931	0.1907	0.1882	0.1868	0.1857	0.1844	0.1827	0.1803	0.1783	0.1766	0.1762	0.1776	0.1782
239	T11	0.0312	0.0325	0.0339	0.0338	0.0341	0.0342	0.0342	0.0341	0.0338	0.0336	0.0333	0.0328	0.0327	0.0323	0.0322	0.0320	0.0319	0.0316	0.0312	0.0310	0.0306	0.0302	0.0299	0.0297	0.0296	0.0297	0.0298	0.0300	0.0305	0.0307	0.0307	0.0308	0.0308	0.0308	0.0308	0.0313
240	T12	0.1389	0.1988	0.3755	0.6293	0.7715	0.8018	0.8054	0.8059	0.8059	0.8042	0.8025	0.8017	0.7988	0.7967	0.7964	0.7947	0.7936	0.7913	0.7871	0.7872	0.7839	0.7803	0.7757	0.7707	0.7677	0.7640	0.7640	0.7657	0.7675	0.7665	0.7652	0.7653	0.7657	0.7670	0.7705	0.7773
END_DATA
    

The patch measurements follow the BEGIN_DATA line, one per line. Each line begins with the data line number, followed by an identifier indicating the column (A through T) and the row (1 through 12), which is followed by the spectral measurement data for the patch. Each measurement consists of 36 numbers, which represent the spectral responses from 380 through 730 nm at 10 nm intervals.

The beginning and ending of a reference file in the non-spectral format is shown here:

Date: 3/27/2000  Time: 19:04						
LGOROWLENGTH 12						
BEGIN_DATA_FORMAT						
Sample_Name	XYZ_X	XYZ_Y	XYZ_Z	Lab_L	Lab_a	Lab_b
END_DATA_FORMAT						
BEGIN_DATA						
A1   	74.79	77.56	64.46	90.58	0.01	-0.46
A2   	3.08	3.19	2.77	20.8	0.05	-1.05
A3   	18.98	19.71	16.53	51.51	-0.15	-0.64
A4   	74.57	77.34	64.38	90.48	-0.01	-0.55
A5   	3.1	3.21	2.78	20.87	0.03	-1.07
A6   	18.88	19.62	16.44	51.4	-0.15	-0.62
A7   	74.65	77.43	64.37	90.52	-0.03	-0.47
A8   	3.05	3.16	2.74	20.69	0.03	-1.06
A9   	18.86	19.59	16.42	51.37	-0.15	-0.63
A10  	74.33	77.13	64.18	90.38	-0.07	-0.53
A11  	3.05	3.16	2.74	20.68	0.06	-1.07
A12  	18.94	19.67	16.48	51.46	-0.14	-0.6
B1   	18.98	19.71	16.53	51.51	-0.15	-0.63
B2   	9.28	6.32	3.27	30.2	29.98	11.49
...
S10  	17.03	7.57	3.05	33.07	69	17.97
S11  	6.56	11.29	24.29	40.07	-37.61	-36.38
S12  	18.91	19.64	16.46	51.43	-0.15	-0.61
T1   	18.91	19.64	16.46	51.43	-0.15	-0.62
T2   	3.05	3.16	2.73	20.67	0.06	-1.02
T3   	74.38	77.15	64.2	90.39	-0.01	-0.54
T4   	18.94	19.68	16.48	51.47	-0.15	-0.6
T5   	3.12	3.24	2.79	20.97	0.02	-0.96
T6   	74.2	76.97	63.98	90.31	-0.03	-0.46
T7   	18.87	19.61	16.43	51.39	-0.16	-0.62
T8   	3.04	3.16	2.73	20.66	0.02	-1.04
T9   	74.41	77.19	64.05	90.41	-0.03	-0.36
T10  	18.9	19.63	16.46	51.42	-0.15	-0.62
T11  	3.09	3.2	2.78	20.82	0.05	-1.1
T12  	74.57	77.32	64.19	90.47	0.03	-0.39
END_DATA						
    

The patch measurements follow the BEGIN_DATA line and are presented as seven items per line. The first is the identifier indicating the column (A through F) and the row (1 through 4). The next three items are numbers representing the XYZ values for the patch (relative to the CIE 2° standard observer and the CIE D50 reference illuminant). The last three items are the numbers representing the CIE Lab values for the color.

Your measuring instrument may have come with software that can create a file in one of these formats. If not, the easiest way to make a custom reference file that can be used with inCamera, is to copy the file that is included with inCamera, and then edit it with any text editor that can save plain (unformatted) text files.

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