Understanding Metamerism

Metameric Failure

Have you ever had a customer complain that the color of a print job is not what they wanted? If the job was printed via inkjet, perhaps a clogged nozzle is the culprit of the unwanted color shift. Also, improper color management, like not using the correct output profile (printer, paper, inkset, resolution) can certainly create a print with noticeable color shift as well. These issues are easily remedied because both you and the customer should be able to see that the print is not what it should be, color-wise that is.

But what about when you think the color is perfect and the customer doesn’t agree with you? Many times this can lead to a falling out between you and your customer and you could jeopardize future business. You don’t want to pay to re-print a job that, to you, looks perfect. And they don’t want to pay for a job that they feel is not up to their standards. What do you do?

Blame metameric failure! If you have been in the industry for some time you have no doubt heard the term metamerism used before. However, there is a lot of misinformation out there regarding this term.

The purpose of this article is to clearly define the three types of metameric failure so that you can identify them in the field. Once identified, there are simple solutions to resolve this conflict with your clients. These solutions should not only repair what rift may have been created in the first place, but also reinforce why they chose you to print the job in the first place.

So what is metameric failure? In the simplest terms, it is when two colors that are supposed to look alike don’t. There are three different types of metameric failure: illuminant, observer, and field size.

Illuminant Metameric Failure

Illuminant Metameric failure is when two colors look the same under one light source, but look different in another. Let’s say you have 5000 Kelvin bulbs in your print shop and that is how all of your prints are evaluated. The prints look perfect in your shop, but after your customer gets the job delivered, he calls and tells you the colors are not right.

He may be viewing the print under incandescent lights, which are typically around 2600 Kelvin. He says that all of your grays look like they are red or yellow, and not neutral gray.

The first step in solving this failure is to ask him what type of light source he is using to evaluate the prints. If he answers with incandescent, halogen, warm white, or any other warmer type of bulbs (see Figure 1), that could be the culprit. There are two things you can do to help address this issue: one is the cheap way out and the other is a bit more expensive.

Figure 1: Because different light sources emit different color temperatures, evaluating the accuracy of a color print for your client can be difficult. (Illustration courtesy of Specialty Optical Systems, Inc., Dallas)

The cheap solution (if you use 5000K as a standard) is to tell you customer to take the print outside. Since 5000K is the temperature of daylight, the print should look perfect out there. A good idea is to have a disclaimer on your website that says that your prints are printed to look ideal in daylight (5000K), but colors may shift if they are in different light sources. You can even go as far as to put hyperlinks on your website to where you customers can purchase 5000K bulbs so that they can see what you see, and obviously you can go over this with them in the proofing stage and physically show how color works in different lighting situations.

The more costly solution is to upgrade your printer. Many older inkjet printers (over six years old or older) had inks that struggled with staying consistent in different lighting sources. However, the newest inks in today’s inkjet printers have drastically reduced the amount that their inks will change in different lighting conditions.

While this may not be reason enough alone to justify the expense, you should also check out how inexpensive new printers can be, how much faster they print now, and how much larger the color gamut is. All of this together should tell you it is time to upgrade.

Observer Metameric Failure

This type of failure is a result of difference in color vision between observers. Color blindness is a common cause of this, but it can happen between two people with normal eyes. Have you ever had an argument with someone over the color of an object? You say blue, they say green, but you agree on hazel because, ultimately, it describes both. There are many physical characteristics of the human eye that vary from one person to the next that cause us to see things differently. The solution to this is simple… Remove human error.

A very basic spectroscope can be made from cardboard with a narrow slit, a prism and a light source. Even this simple instrument reveals a clear difference in the visible spectrum of different light sources—in this case comparing a conventional incandescent lamp with and arc discharge-based lamp. (Image courtesy of Tim Wether)

If you have a spectrophotometer, like the X-rite i1, and the freeware i1 Share, then you can read any printed color and get the LAB value. Most design and image software, such as Adobe Illustrator or Photoshop will have an info pallet where you can check the LAB value of any color with the color picker (see Figure 2). You should be able to see in Delta E, the difference between the file and the printed image. (You must soft proof in Photoshop or illustrator for the output profile for this to be accurate.)

Figure 2: Most design and image software, such as Adobe Illustrator or Photoshop, will have an info pallet where you can check the LAB value of any color with the color picker.

Any Delta E value of five or under is not noticeable to the average human. By using a spectrophotometer, you eliminate the human factor and you’re relying on math for an objective answer. Numbers never lie.

Field-Size Metameric Failure

This type of failure occurs because our eyes see color differently if it is the center of our vision, when compared to how color is perceived in your peripheral vision.

You may run into this if you are in the grand format world. Your customer may submit a file they have designed to be a huge banner or billboard. They are accustomed to looking at the file on a computer screen that is in the center of their vision.
However, you print the file to be 60 feet by 15 feet. Your customer complains that the colors look different. It could be that they are standing too close to the print, and their peripheral vision is changing the color in their mind.

You can either have the customer stand back farther, or you could again use a spectrophotometer to take LAB values of the colors in question to prove to them that it is within an acceptable range.

You should now be better armed to handle the situation when you and your customer don’t see eye to eye on color. My advice is to take the time to educate the customer about metameric failure, use the associated solution to come to an agreement, and establish yourself as the color guru they will always want to rely on for all of their printing needs.