color matching
2009-07-19 by Dave Sainsbury
No complaints with the output from my Epson 4880 printer with Ilford Smooth Pearl paper using the profile made and tweaked. I just wish I knew why I needed to tweak Did the full Spyderprint3 process to make the printer profile. Used the software to measure my Macbeth color Checker Rounded these numbers off and made a card in the virtual space of Photoshop using the Lab values. Printer this off using the new profile. (perceptual intent with black point compensation) Scanned the resultant printout to get objective proof of my visual impression The printout was too dark Rebuilt the profile with +10 Brightness and printed out again. Scanned this printout to confirm that I had lost "punch" Rebuilt the profile with +10 brightness, +10 contrast. Output better again as confirmed by a rescan. Calculated the differences between printouts using CIE2000 formulae. Data below. Finally my question: Why did the first printout come out too dark? Is there a more scientific way of scanning printouts and using the results to tweak the profile? Dave Values used off card to make photshop image My measured values off card No adjustments Brightness+10 Brightness+10, contrast+10 1 39.24 14.02 15.4 39 14 15 33.88 14.08 14.92 40.93 14.73 11.71 38.12 16.86 12.39 2 65.72 19.36 16.6 66 19 17 59.79 20.58 14.36 64.58 18.52 14.33 66.43 20.49 18.3 3 50.14 -4.39 -22.85 50 -4 -23 44 -3.46 -24.24 51.21 -2.47 -22.42 49.25 -4.09 -28.01 4 44.53 -16.69 24.6 45 -17 25 39.02 -15.21 21.99 45.59 -14.63 24.87 43.16 -17.01 24.49 5 55.43 9.63 -25.8 55 10 -26 49.53 11.29 -26.94 55.38 9.96 -24.41 55.38 11.55 -28.98 6 71.16 -32.87 -0.81 71 -33 -1 64.41 -30.79 -3.78 69.36 -28.57 -0.87 71.77 -33.16 -1.89 7 64 35.37 60.89 64 35 61 56.98 36.74 62.01 61.62 32.13 57.82 62.88 36.64 59.53 8 40.17 10.22 -46.36 40 10 -46 35.71 12.31 -46.73 42.16 8.83 -42.74 38.59 12.95 -51.77 9 50.78 47.76 15.79 51 48 16 45.56 46.67 14.06 51.16 44.47 14.43 51.07 52.59 19.39 10 32.14 21.88 -19.45 32 22 -19 28.85 22.19 -19.24 34.46 19.31 -18.44 31 22.22 -22.16 11 73.38 -24.28 58.37 73 -24 58 65.09 -22.02 57.09 69.05 -20.7 50.89 71.31 -22.3 60.44 12 73.03 17.99 73.52 73 18 74 65.29 19.98 72.48 69.44 15.94 68.04 71.5 14.76 76.27 13 28.2 13.5 -50.61 28 14 -51 28.67 17.98 -44.5 30.71 10.51 -49.14 27.63 17.54 -55.96 14 55.86 -37.63 32.27 56 -38 32 49.13 -36.3 29.64 55.06 -33.04 28.11 55.4 -42.18 33.51 15 43.58 55.69 30.05 44 56 30 39.97 53.19 28.29 44.69 52.67 28.3 45.12 59.66 32.99 16 83.55 2.71 82.58 84 3 83 76.08 5.93 81.49 74.5 -9.89 76.38 80.18 1.07 83.15 17 52.08 53.09 -14.4 52 53 -14 46.58 51.89 -14.3 52.41 49.23 -13.17 52.42 58.76 -15.19 18 50.31 -27.66 -30.08 50 -28 -30 43.86 -26.32 -32.11 50.55 -25.24 -29.02 50.2 -27.89 -34.58 19 96.59 0.5 0.64 97 1 1 91.01 2.02 -1.05 91.54 2.29 0.5 91.89 0.86 0.91 20 81.37 0.16 -0.63 81 0 -1 75.68 0.97 -1.9 78.12 1.22 -0.9 80.56 1.75 -0.78 21 66.64 -0.4 -0.92 67 0 -1 61.03 1.85 -3.01 65.55 1.56 -1.41 68.42 1.63 -1.41 22 50.8 -0.02 -0.28 51 0 0 45.92 0.77 0.08 51.48 1.3 -1.18 50.86 2.36 -1.85 23 35.56 -0.12 -1.72 36 0 -2 31.77 0.17 -0.67 38.47 0.91 -1.43 34.49 0.17 -1.8 24 21.45 0.61 -1.33 21 1 -1 20.08 3.68 -3.76 26.06 2.46 -2.05 21.1 0.59 -0.5