Colour calibration card
A color calibration card ( 1 ) for digital photography with a maximum of 40 calibration fields, each exhibiting a color in a color space according to CIE 1976 (L*, a*, b*) D50 2°, wherein a first group with at least 3 calibration fields ( 4 G1 , 4 G2 , 4 G3 ) exhibits green colors having an a value within the range of −30 to −60 and a b value within the range of +10 to +30, a second group ( 4 B1 , 4 B2 , 4 B3 ) exhibits blue colors having an a value within the range of −20 to −20 and a b value within the range of −30 till −60, a third group ( 4 R1 , 4 R2 , 4 R3 ) exhibits red colors having an a value within the range of +40 to +60 and a b value within the range of −5 to +30, and wherein the respective calibration fields in each group ( 4 G1 , 4 G2 , 4 G3 ; 4 B1 , 4 B2 , 4 B3 ; 4 R1 , 4 R2 , 4 R3 ) exhibit colors for which the values in at least one of a or b differ by at least 5 units from the corresponding values for the other calibration fields in the group.
1. A color calibration card for digital photography, which comprises:
a printable substrate with a designated front side and a back side, wherein said front side exhibits a maximum of 40 calibration fields which each exhibit a color in a color space according to CIE 1976 (L*, a*, b*) D50 2°, wherein a number of the calibration fields have been selected in such a way that said front side exhibits a first group with at least 3 calibration fields ( 4 G1 , 4 G2 , 4 G3 ) exhibiting respective green colors in said color space having an a value within the range of −30 to −60 and a b value within the range of +10 to +30,
a second group with at least 3 calibration fields ( 4 B1 , 4 B2 , 4 B3 ) exhibiting respective blue colors in said color space having an a value within the range of −20 to +20 and a b value within the range of −30 to −60,
a third group with at least 3 calibration fields ( 4 R1 , 4 R2 , 4 R3 ) exhibiting respective red colors in said color space having an a value within the range of +40 to +60 and a b value within the range of −5 to +30, and that the respective calibration fields in each group ( 4 G1 , 4 G2 , 4 G3 ; 4 B1 , 4 B2 , 4 B3 ; 4 r1 , 4 R2 , 4 R3 ) exhibit colors for which the values in at least one of the coordinates a or b differ by at least 5 units from the corresponding values for the other calibration fields in the same group, whereby said three green, blue and red colors, respectively, of the calibration fields have been selected in the region where it is expected to find a digital camera's sensitivity peak to the respective color, and with a defined interval between the respective calibration fields in each group, to provide an improved color calibration result by means of said color calibration card in digital photography.
2. The color calibration card according to claim 1 , wherein the colors of the calibration fields have been selected from the quadrants (R-Y; Y-G; G-B; B-R) in a color circle, so that said plurality of calibration fields, from each quadrant, exhibits at least one first color (RY 1 ; YG 1 ; GB 1 ; BR 1 ) having a first color saturation (C 1 ), and at least one second color (RY 2 ; G 1 ; GB 2 ; BR 2 ) having a second color saturation (C 2 ), wherein the first color saturation (C 1 ) is no more than 60% of the second color saturation (C 2 ).
3. The color calibration card according to claim 1 , wherein said plurality of calibration fields comprises at least 2 calibration fields ( 4 YG1 ; 4 BR2 ; 4 GB2 ) exhibiting colors from the intermediate color groups Red/Green (RG 1 ), Blue/Red (BR 2 ), Green/Blue (GB 2 ).
4. The color calibration card according to claim 1 , wherein said plurality of calibration fields comprises at least 3 calibration fields exhibiting colors from the intermediate color group Red/Green.
5. The color calibration card according to claim 1 , wherein said plurality of calibration fields comprises at least 3 calibration fields ( 4 Bw1 , 4 BW2 , 4 BW3 ) providing a grey scale.
6. The color calibration card according to claim 1 , wherein the color calibration card also exhibits a plurality of data fields ( 5 R3 , 5 GB1 , 5 RG1 ) for “Lab values” according to CIE 1976 (L*, a*, b*) D50 2°, corresponding to the respective colors (R 3 , GB 1 , RG 1 ) of said calibration fields ( 4 R3 , 4 GR1 , 4 RG1 ).
7. The color calibration card according to claim 6 , wherein said data fields are provided on a different surface of the calibration card than the designated front side.
8. The color calibration card according to claim 6 , wherein said data fields are provided on a back side of the calibration card.
9. The color calibration card according to claim 1 , wherein the color calibration card exhibits at least one information field for text or other information.
10. The color calibration card according to claim 1 , wherein the front side of the color calibration card exhibits corner markings for facilitating adjustment of the camera before color calibration.
11. The color calibration card according to claim 1 , wherein the front side of the color calibration card exhibits corner markings in the form of black and white circle patterns for facilitating adjustment of the camera before color calibration.
12. The color calibration card according to claim 1 , wherein the color calibration card is designed in an A4 format or smaller.
13. The color calibration card according to claim 1 , wherein the color calibration card has a weight lower than 100 grams.