Idaho Airships, Inc.

In photometry, colors that have a similar visual character as sensed by a normalized human eye, but actually have differing spectral componentry are referred to as “Metamers.” If you are frustrated by the apparent colors of your prints varying under different kinds of lighting, it is possible that you are afflicted with Metamerism. My loving bride just handed me an experimental dessert laced with Cognac-this post may start to ramble.

Red, Green and Blue (the primary colors, the irreducible components of visible range electromagnetic energy, or “light”) can exist in a wide variety of ratios. Some of those ratios may appear to the normalized human eye as exactly the same color even though they are of dissimilar compounding.

Don’t believe me? Take a look at this.

When you print, you are actually laying down inks that contain pigments (for archival inks) or dyes which themselves possess individual spectral reflectance properties. The ink drops combine (they actually don’t sit on top of each other-they rely on the inability of the viewer to distinguish them because they are so small) to produce the appearance of particular colors. The ratios of fundamental ink colors are only perceptually accurate at a certain, particular Color Temperature.

You already know a bit about Color Temperature, and you are aware that various types of lighting (such as flourescent and incandescent bulbs) have very different Color Temperatures than outdoor light. It is very probable that the light in your office or print room is quite different than the types of lighting under which your prints will be viewed.

That, in fact, is the problem.

To be fair, Metamerism is much more pronounced in pigmented (“archival”) inks than in dye inks, but over the past few printer generations (since about 2003) Metameric problems have been drastically reduced. It has not, however, been reduced to the point of irrelevance, particularly in applications where a print may be afforded more than ordinary scrutiny such as in an art show, jury trial, or even a customer’s Board Room where various prints from a number of photographers are spread out across a table in a room with mixed flourescent and quartz lighting and large, south facing windows.

I’m trying to establish the idea that understanding and controlling (to the extent possible) Metamerism offers substantial competitive benefits.

By the way, poorly prepared images-particularly those with insufficient Contrast-can be problematic in a way that is easily confused with Metamerism. Thus, resolving Metamerism doesn’t necessarily guarantee a crystalline print.

How do we therapeutically address Metamerism?

The first step is to institute a Color Management System (CMS) into your workflow. I have my monitors calibrated and profiled under daylight (5500K) conditions, which is a point of contention with many because optical brighteners used in print media tend to perform more reliably under 6500K ambience. My CMS policies are sound and my knowledge of digital preparation is pretty fair as well-these are all capabilities that must be developed in order to offer a comprehensively virtuous workflow (remember “A Chain is Only as Strong as It’s Weakest Link?”).

The second step is to proof your prints under their actual display conditions, when possible. Yes, this can be tedious and expensive…a good viewing booth can run into the several thousands of dollars. More modest systems are quite reasonable-I have a daylight broad lamp set up in an otherwise poorly lit area of my office. Ideal proofing light intensity and Color Temperature accuracy requirements remain topics of great contention, in part because there is no economical way to truly isolate either element in both preparation and display.

Finally, since simply viewing a print really doesn’t resolve any problems, it may be necessary to adjust the color formulation of the image if Metameric or other corruptive influences have risen to the level of “objectionable.” This obviously requires a trained “eye” and an understanding of the preparation process beginning with your CMS, but also your understanding of Contrast and general color theory. Corrective measures for Metameric corruption far exceed this post, and to be honest, I’m unaware of any definitive “cookbook” for Metameric resolution. It may be more “art” than “science,” and it is yet another reason that engaging the science beneath your craft is something to be honored.

Incidentally, images prepared for monitor display (vice print) should be prepared at 6500K, which represents a reasonable compromise between 5000K and ~7000K-the approximate nature of an uncalibrated PC monitor…which is unfortunately the condition under which your online images will find themselves most frequently displayed.

L