January 2010 — Issue #5
Colorimetry I say tomato, you say tom-aah-toe. I say red, you say red. But these reds don’t match, they’re different shades of red – so who’s right? Wikipedia defines colorimetry as "the science and technology used to quantify and describe physically the human color perception. Huh? More simply put, how do you see color? How do I see color? Do we agree that, that color is the same or different, and either way, is there some science, technology or other standard that we can apply to actually measure that individual subjectivity? Color perception is a bit like lawyers. Ask three and you’ll get four different answers, maybe more. The short answer is yes there is a way to measure and quantify color. Why spend time writing about this? Because it’s what we do, even though you as a customer may not even realize it or even know how important it is. But if this piece is missing, I can almost guarantee you’ll notice. Most of our customers are at least vaguely familiar with the Pantone Matching System (PMS). Many even have their own PMS books. Have you ever compared your PMS book to another one – regardless of age? It’s likely you see at least some noticeable difference in the very same color between books. Some colors more difference, some less. Why is that? Even PMS books are printed colors. Printed by different printers in different environments, different times, under different conditions and so on. End result – variation – some noticeable, some not so much. So how do you minimize that variation and/or get repeatable consistency? It’s not my intention in this short writing to give you a full accounting of colorimetry, just a snapshot of what it does and why it’s important. Color can actually be measured using an instrument (a Spectrodensitometer) that defines three variables, hue, chroma and value or lightness. Laymen’s terms; color is defined the way the human eye sees color, only digitally. Those variables are measured by the instrument calculating mathematical formulas resulting in a “digital string”. This “digital string” then defines that certain color. Sort of like the GPS coordinates for that color within the digital color space universe. Clear as mud? That’s why we use the instrument. So moving right along, how does this work? We measure the color using the instrument. It provides the resultant “digital string”. Is that the correct color? Maybe. While you have the “GPS” coordinates of that color, what you are really measuring for is a range that the color falls within. It’s nearly impossible to exactly duplicate color every time it’s printed, so a range is necessary. How close is my color to the color we are trying to get? That’s the key, and that range is defined as a delta E. Delta E is what results when the instrument number crunches all the variables within the “digital string.” A delta E of one, is the smallest color shift that the human eye can detect. As printers, a color range of up to three or four delta E’s is typical. A delta E of two is usually considered a very tight spec. However some colors may range up to around four and still look the “same”. That’s because the human eye also sees each color differently. In other words take beiges and grays; in these shades the eye can detect a color shift almost immediately, so a delta E of 3.5 will be immediately noticeable. Whereas with a red, which is very forgiving, you may have a delta E of 3.5 and agree that it is a “match”. Delta E is not a +/- amount or percentage difference. It simply helps define a comparison range between two colors and how the eye sees those colors. And it is different for all colors. Here at Columbine Label Company, we try to hold these ranges as near to around two or less as possible. So all that said (and understood I’m sure!) what’s the point? Repeatability and understanding. Each printing is now measurable, repeatable and matches the previous printing. If you simply printed each job and eyeballed it to the last job printed and each job is a half shade off – what do you have at the end of 4 or 5 printings? Labels that don’t match the one next to it on the retail shelf, that’s what. Now maybe one looks old or faded, because it’s not the same as its neighbor. Do you want that product rejected because it’s not selling? We’ve also encountered occasions where we needed to match some other printed item like a box. Customer says my PMS color is 200, when in fact it’s really printed to match 185. Do you want us to match your PMS 200 spec? or the previously printed “matching” piece that’s really a different shade at 185? Most want the two to match, but we will do what you instruct us to do; unless we both understand that what we want and what we are asking for are two different things. Hopefully that all makes a bit of sense. It’s also why we tend to ask a lot of questions. At Columbine Label Company we take a lot of pride in doing a job the way we would want it done if we were paying the bill. So is your red just red? Or is it your red? Paying attention to the details and having the proper tools to do the job are no small pieces of the puzzle, no matter how transparent they may be to our customers. Just one more reason:
Quotable Quotes"Politics is not a bad profession. If you succeed there are many rewards, if you disgrace yourself you can always write a book." "Do or do not. There is no try." "We judge ourselves by what we feel capable of doing, while others judge us by what we have already done." History in January:
Stick with The Columbine Label Company; we stand behind our service, quality and commitment to you. Contact us today for any label or packaging need.866-610-0804
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