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Issue #5 Welcome to ColorNews, a periodic update on all things related to Color Management. Please let us know what your interests are so we can address these concerns in our coming issues. We apologize for the delay from our last newsletter, many exciting changes have taken place at CHROMiX and we will be covering them over the next few newsletters. ColorNews covers newsworthy items including new product releases and updates, and interesting, informative web sites. Each issue willinclude a feature article covering an aspect of color management such as profiles, workflow, and so forth. In a visit to CHROMiX.com or profilecentral.com, you opted to receive this newsletter. You may have also heard Steve Upton speak and requested more information. If you have received this message in error, we apologize. We value our relationship with you and do not want to spam you. See below for details on how to provide feedback, how to unsubscribe, or how to become a sponsor. Table of Contents 1. CHROMiX News CHROMiX News There have been so many changes at CHROMiX since the last newsletter that it is worth mentioning them here:
Staffing - we have had several staffing changes over the last months but one we are really excited about is the addition of Rick Hatmaker. Rick has many years experience in the computing, digital imaging and color management markets and is now acting in a sales and system consulting role for us. Call him toll free at 877-colorgear x7 or hatmaker@chromix.com. He's eager to put his talents to work solving your color problems. Offices - CHROMiX has moved into larger offices in Seattle to accommodate our growth. Our mailing address and phone numbers remain the same but the new space will accommodate our expanding profile-building lab and we are planning on holding small hands-on seminars there as well. We'll let you know more as it develops.
| A D V E R T I S E M E N T | Free monitor hoods with LCD/CRT Spyders and Eye-One systems !! GretagMacbeth has made many announcements over that past few months including:
ColorFAQs Each month, our President Steve Upton will take time to answer questions we receive on a regular basis. If you have specific questions or comments, please see below for how to make submissions. This Month - Metamerism - or Things That Go Weird in the Light. Have you ever compared two garments in a store and decided they matched, only to find that when you left the store and went out into daylight they no longer matched and instead looked quite different? If so, you have seen an optical phenomenon called metamerism (me 'ta merizm). Strictly speaking, metamerism occurs when you see two samples match under one light source (illuminant) and not match under another. How can this be? Well, it comes down to the difference between how an object affects light, and the color it appears to our eyes. Objects affect light by selectively reflecting or absorbing light of different wavelengths. So an object that absorbs most blue wavelengths and reflects most red wavelengths will usually appear red to our eyes. The actual color it appears to us is dependent on the spectral composition of the light reflecting off the object. Let's say, for example, we have two objects that each reflect red light in approximately the same way but one reflects blue light while the other absorbs it. If you put both objects under reddish lighting (and most indoor tungsten lighting falls into this range) then they may appear to be very close to the same color. As there is very little blue light falling on our objects, the difference between their blue reflectiveness is almost invisible. The red reflection is about the same so they both reflect similar wavelengths and our eyes see them as the same color! This would not be a problem if we didn't have many different colors of lighting in everyday life. So let's take our objects outside into mid-afternoon daylight. Sunlight at that time of day contains considerably more blue light than indoor lighting. As before, our pair of objects will reflect red light similarly but one of them will reflect a significant amount of blue light while the other absorbs it. Our eyes will see the blue light from one object combined with the red light and we would probably call the result magenta. Suddenly what we thought were two reddish objects no longer match at all! Is this a problem? That depends. In many ways this very phenomenon is essential to color reproduction (see "Metamerism as Friend" below), but when colors "shift" from our expectations, clients stop paying bills, and that is a problem. Where will we see this problem in the business of digital imaging?
Is there anything we can do about it? 1) Be aware - this isn't really a solution but it is always the first step toward one. 2) Choose pigments carefully. Beware of pigmented inks for inkjet printers (see Pseudo Metamerism below) 3) Control your lighting - both for producing prints and for final viewing, if possible. 4) Profile carefully Can color management using ICC profiles correct for this problem? No... and yes. ICC profiles are typically built using readings referenced to D50 (5000K) lighting. That means that prints created using these profiles will look best under D50 lighting. Viewing them under any other lighting can give unpredictable results. Most printing pigments and dyes have been carefully chosen to not conflict with each other or other pigment sets. One exception that is appearing more and more is pigmented inks for inkjet printers (again, see Pseudo Metamerism below). Sometimes you can measure printed or scan/camera targets with a different light source such as D65 in the calculations. This should make the print viewable optimally under D65 lighting. This is not always successful and requires the appropriate settings to be available both on the instrument and in the software. We are continually experimenting with such techniques to find solutions for our clients. | A D V E R T I S E M E N T | CHROMiX ColorThink - Your brain on color! *** Pseudo Metamerism *** One closely-related problem cropping up more and more often in the inkjet printing world is often (incorrectly) called metamerism. When colorants are mixed carefully in a printer, you can achieve a smooth, neutral gray gradient from black to white. With most inkjet printers, the ink combination will include Cyan, Magenta, and Yellow inks in varying amounts along with Black ink. When properly balanced, pleasing black and white images can be printed. Many users are also experimenting with near-neutral imaging such as adding a slightly blue or sepia tone for effect. With the fugitive nature of dye-based inks, many users are switching to pigment-based inks for the vastly improved permanence. After all, if you are printing and selling works for display, your customers tend to have the expectation that the work will last beyond 2-3 years. Pigmented inks however, can suffer from a pigment balance problem which rears its head in a similar manner to the two-sample metamerism problem. When a quality ICC profile is created for a pigmented ink set, you will typically see a good neutral gray gradient. As mentioned above, ICC profiling assumes the print is viewed under D50 lighting. With some pigment sets (ie CMYK inks sold and/or used together) the gray gradient color shifts considerably when viewed under different illuminants. It is important to note that this is not an expected color shift but rather a shift that appears strange to the eye. One would expect that a gray tone viewed under D50 lighting would appear to be a warmer gray when viewed under warmer, tungsten lighting. The color balance failure we are referring to here shows up as a green or magenta cast and is noticeably different than a shift normally attributed to warmer or cooler light. Many people incorrectly refer to this phenomenon as metamerism. Metamerism, however, is specifically defined as a phenomenon that occurs between two samples. The ink balancing situation does not involve two samples but rather a balance of pigments in one sample. Strictly speaking, then, it is not metamerism and we (at CHROMiX) often refer to the problem as Gray Balance Failure or Color Balance Failure. What can I do to avoid Gray Balance Failure (GBF)? As with the suggestions above there are several things to do to minimize the effects of GBF. 1) Control your lighting - not always possible, but if you can it is often the easiest solution. 2) Choose your pigmented ink set carefully. View them under different lighting conditions to see if they shift considerably. Remember, it is the combination of pigments that is causing the problem. Some users have found success in mixing inks from different vendors such as the black from one set in combination with the colored inks from another. Needless to say, this route can require extensive testing. 3) Profile for different lighting conditions - as mentioned before, this is not often very easy to do. *** Metamerism as Friend *** After all is said and done, it is fair to say that metamerism is our enemy, right? Not so fast... Metamerism, remember is when an object matches another under a certain illuminant even though the spectral characteristics of the two objects differ. The act of balancing three or four colorants (such as CMYK inks) so they appear to be the same color as an original object is also based on metamerism. Because of the 3-channel nature of our eyes, we can get 4 inks to appear to match a real-world object like a person's face without the spectral characteristics of the inks resembling the face much at all. This means that the printand the face affect light differently but appear to be the same color to our eyes! This is the basis of digital imaging and printing today. It is fair to say, then, that without metamerism we would not be able to do ANY of the imaging we do today! It is only when the balance fails that we call it a problem. Perhaps a match-failure problem should be called metamerism "failure" rather than metamerism, but this term does not seem to be used at all. In closing... As with anything in the color management world, being aware of the problem is half the battle. Now that you know about metamerism and GBF you can consider it as a contributing factor when things don't look right. Also, if you have no D50 lighting under which to view your prints it is possible they will never look quite right. Invest in controlled lighting for print viewing. With the many variables in digital color work that can give you problems, nailing down lighting is considered a basic requirement for print viewing as well as monitor to print matching (see ColorNews issue #2). FEEDBACK and FAQs |
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