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Hi folks!
We are getting quite a database of reflectance data from different paints, but we mix developers don't have the mathematical skills required to accurately predict how two colors will interact when combined.
When someone has a color computer-matched at a paint store, what happens is that the color is measured by a spectrophotometer which breaks down the color into a range of spectral reflectance readings. The computer software then uses it's database of the same type of spectral readings of the tints available and the base chosen to mix the final color. For light to medium dark colors this process results in an amazingly close match (it has failed for VERY dark colors).
While the goal would be to ultimately be able to combine two or more colors via software and get a correct prediction of the color that would be produced, what we are starting out with is simply adding a gray paint to a white paint and getting the resulting gray shade correct. We are using an Excel spreadsheet to do the figuring.
EXAMPLE DATA
To show what we are up against, I will give a list of reflectance data for a white paint, a gray paint and then the REAL combination when joined in equal amounts.
The numbers on the left (400-700) represent the color of the light measured in nanometers; 400 nm is deep violet, 700 is deep red.
The numbers on the right are the percentage of reflectance (0-100) of that color.
Valspar Ultra Premium Enamel flat White
400 42.99
410 66.58
420 82.98
430 89.47
440 90.4
450 90.19
460 89.48
470 89.76
480 90.4
490 91.24
500 91.96
510 92.01
520 91.83
530 91.94
540 92.19
550 92.53
560 92.9
570 93.33
580 93.6
590 93.24
600 92.8
610 92.98
620 93.46
630 94.32
640 94.86
650 93.92
660 92.79
670 92.58
680 92.85
690 93.48
700 94.49
Behr #1850 in 'Reference Gray'
400 36.9
410 45.3
420 50.79
430 52.18
440 51.5
450 50.92
460 50.42
470 50.2
480 50.16
490 50.39
500 50.66
510 50.66
520 50.57
530 50.55
540 50.6
550 50.75
560 50.95
570 51.2
580 51.39
590 51.3
600 51.09
610 50.89
620 50.72
630 50.71
640 50.6
650 50.01
660 49.33
670 48.88
680 48.61
690 48.55
700 48.69
The measured combination mixed 1:1
400 40.27
410 52.92
420 61.26
430 63.46
440 62.6
450 61.99
460 61.5
470 61.36
480 61.38
490 61.5
500 61.63
510 61.65
520 61.63
530 61.65
540 61.68
550 61.65
560 61.68
570 62.02
580 62.35
590 62.24
600 61.96
610 61.77
620 61.62
630 61.59
640 61.46
650 60.91
660 60.3
670 59.89
680 59.65
690 59.58
700 59.67
While math is not my strong suite, I have tried taking the arithmetic mean, geometric mean and harmonic mean of the white and gray paints, but none of them match the measured result. I'm at the end of my rope and am stuck firmly in the mud. :dizzy:
I'm hoping someone out there has the ability and willingness to help us figure out how to do this. If those reading this don't have one or the other, but know someone that might, please ask them!
raying:
We are getting quite a database of reflectance data from different paints, but we mix developers don't have the mathematical skills required to accurately predict how two colors will interact when combined.
When someone has a color computer-matched at a paint store, what happens is that the color is measured by a spectrophotometer which breaks down the color into a range of spectral reflectance readings. The computer software then uses it's database of the same type of spectral readings of the tints available and the base chosen to mix the final color. For light to medium dark colors this process results in an amazingly close match (it has failed for VERY dark colors).
While the goal would be to ultimately be able to combine two or more colors via software and get a correct prediction of the color that would be produced, what we are starting out with is simply adding a gray paint to a white paint and getting the resulting gray shade correct. We are using an Excel spreadsheet to do the figuring.
EXAMPLE DATA
To show what we are up against, I will give a list of reflectance data for a white paint, a gray paint and then the REAL combination when joined in equal amounts.
The numbers on the left (400-700) represent the color of the light measured in nanometers; 400 nm is deep violet, 700 is deep red.
The numbers on the right are the percentage of reflectance (0-100) of that color.
Valspar Ultra Premium Enamel flat White
400 42.99
410 66.58
420 82.98
430 89.47
440 90.4
450 90.19
460 89.48
470 89.76
480 90.4
490 91.24
500 91.96
510 92.01
520 91.83
530 91.94
540 92.19
550 92.53
560 92.9
570 93.33
580 93.6
590 93.24
600 92.8
610 92.98
620 93.46
630 94.32
640 94.86
650 93.92
660 92.79
670 92.58
680 92.85
690 93.48
700 94.49
Behr #1850 in 'Reference Gray'
400 36.9
410 45.3
420 50.79
430 52.18
440 51.5
450 50.92
460 50.42
470 50.2
480 50.16
490 50.39
500 50.66
510 50.66
520 50.57
530 50.55
540 50.6
550 50.75
560 50.95
570 51.2
580 51.39
590 51.3
600 51.09
610 50.89
620 50.72
630 50.71
640 50.6
650 50.01
660 49.33
670 48.88
680 48.61
690 48.55
700 48.69
The measured combination mixed 1:1
400 40.27
410 52.92
420 61.26
430 63.46
440 62.6
450 61.99
460 61.5
470 61.36
480 61.38
490 61.5
500 61.63
510 61.65
520 61.63
530 61.65
540 61.68
550 61.65
560 61.68
570 62.02
580 62.35
590 62.24
600 61.96
610 61.77
620 61.62
630 61.59
640 61.46
650 60.91
660 60.3
670 59.89
680 59.65
690 59.58
700 59.67
While math is not my strong suite, I have tried taking the arithmetic mean, geometric mean and harmonic mean of the white and gray paints, but none of them match the measured result. I'm at the end of my rope and am stuck firmly in the mud. :dizzy:
I'm hoping someone out there has the ability and willingness to help us figure out how to do this. If those reading this don't have one or the other, but know someone that might, please ask them!