The color space most of us are familiar with is RGB, or red, green and blue, which is an additive model – adding different amounts of each color creates a specific hue. The problem is that RGB doesn’t define what red, green and blue mean.
Last week we discussed the Lyson Continuous Ink System, which we are very impressed with. We concluded with the note that we had attempted to fine-tune the output color profiles and managed to screw them up royally.
A couple of calls to Lyson’s chief support manager, Ken Holtane, got us sorted out. It turns out that two things were wrong – Lyson’s documentation for OS X 10.4 wasn’t accurate (to be fixed soon), and we had misunderstood how color profiles are implemented under OS X.
Last week, for a good reason, we didn’t explain what color profiles are. Such a discussion could occupy every Gearhead for the next six months even if we were attempting to cover just the basics (see the Wikipedia entry).
For this reason, we are going to simplify the topic: A color profile is the range of colors that a given reproduction system (such as a monitor or a printer) can display from the entire range of possible colors.
The color space most of us are familiar with is RGB, or red, green and blue, which is an additive model – adding different amounts of each color creates a specific hue.
The problem is that RGB doesn’t define what red, green and blue mean. For that, we need to turn to absolute color spaces, such as standard RGB (sRGB) or Adobe RGB, which define exactly the meanings of each of the primary colors in terms of the CIE 1931 color space (again, see the very good Wikipedia article).
So, your monitor has a color profile that is peculiar. It is peculiar not only to the brand but also to that individual monitor. If you set up your monitor properly using a tool such as Adobe Gamma, which is installed with Adobe products such as Photoshop, then you will be creating an International Color Consortium (ICC) profile.
This profile provides the data that changes the color space used by, say, Photoshop, into the color space of the display. This means the colors shown on the display will be perceptually the same as when the image is on another display that has also been properly profiled.
When you import, say, a JPEG photograph, it has its own color space called YCbCr, which is used for video systems (see the Wikipedia entry).
Programs such as Photoshop have to translate the YCbCr color space into the color space they use (typically, sRGB or Adobe RGB 1998) and correct for the display’s characteristics using the ICC profile.
So far so good, but now we want to print. Printers such as the Canon i9900, which we discussed last week, have their own color-management systems, and they know the characteristics of the inks they are supposed to use.
But when you use different inks, as we wanted to, you have to tell the printer to mind its own business and not make any color corrections, and tell Photoshop what printer profile to use. In other words, Photoshop has to translate the color space it is using, such as sRGB, into the color space that the printer can render.
In the case of the Lyson Fotonic inks we wanted to use with our Canon i9900, Lyson provides profiles for inks for a variety of paper types, such as satin, gloss and luster. The reason for a profile for each type is that the paper’s reflectivity, ink absorbency and other optical and printing characteristics change how the color appears when printed.
In short – a goal that this column has completely failed to realize – color correcting for display and print is a technically complex subject. On the other hand, providing you at least understand how color workflow operates – that is, the translation from one media to another, for a given combination of software, printer, ink and paper – you should be able to reliably achieve a high level of color fidelity.
Let us know how you do by e-mailing gearhead@gibbs.com. We end this week with a question: What causes Windows to stop showing the Start menu or any grouped entries in the Start task bar? This is happening frequently on one of our PCs, and we cannot find out what the problem is.
