If you’ve ever used a spectrophotometer for color QC, you probably have a general idea of how it works: measure a standard or use a stored one, then measure the sample. The color difference is calculated, and if that difference falls below a certain level it means the sample is a good color match to the standard, and the product is ready to be shipped. The assumption here is that any parts that are a good color match to the standard will also be a good color match to each other, and this is unfortunately not true. Two samples can be a good match to the standard, both visually and instrumentally, but may not be an acceptable match to each other. This is where the panel match function comes in.
Take a look at the set of three flooring tiles below:
Each tile is labeled on the back with a 1, 2, or 3, and when placed in numeric order as above, they appear to be a good color match to each other. But look what happens when we switch Tiles 2 and 3:
Suddenly the tiles don’t appear to match! Nothing has changed about the tiles themselves, only the configuration in which we’re viewing them. To understand the cause of the apparent mismatch, we look to the color data:
Here we see that Tile 2 is slightly lighter, less green, and less yellow than Tile 1. This trend continues when comparing Tile 3 to Tile 2. However, the color differences between Tiles 1 and 2 are not large enough to be discerned visually, nor are the differences between Tiles 2 and 3. We can see from the table and color plot below that when Tile 2 is used as the standard, Tiles 1 and 3 both fall within tolerance:
However, if we set Tile 1 as the standard:
Suddenly Tile 3 is no longer within tolerance! This explains why the colors appear to match when lined up in numerical order, but when the order is switched such that we are directly comparing tiles 1 and 3, they no longer appear to match. Now suppose Tile 2 is used as the master standard and Tiles 1 and 3 are production parts. Tile 1 would be measured against Tile 2 and found to be an acceptable match, as would Tile 3. When the customer goes to install Tiles 1 and 3 side-by-side however, they would be upset to find that the tiles do not match! This is why when testing parts that will end up being viewed next to each other, it is necessary to compare those parts not only to the master standard, but to each other as well. This is where the panel match function comes in; by using Organizers in BYK-Gardner’s smart-chart software, when a color reading is taken of a sample to compare to the standard, another sample can be selected to compare the reading with as well. This ensures that not only will production parts match the desired color standard, but will also be a good visual match to other samples when viewed in a real-world setting.