Blue Skies and Coke Cans Forever


Hope everyone had a nice Memorial Day Weekend. Here in New England the weather was glorious, and we celebrated by partaking of pure All-American fare: amusement park, little league baseball, ice cream, cookout, and Indiana Jones. The kids marched in the parade down Main St (actually they marched down Route 14, but Main St. sounds better).

We also flew our American flag. It is a gorgeous, top notch flag that feels as good as it looks. It even makes an awesome snapping sound in the wind. I fly the flag only a few days each year, Memorial Day, Flag Day, and July 4th. I’m not patriotic in a traditional sense. In my world, the only version of the “Star Spangled Banner” you’d hear before a baseball game is the one by Jimi Hendrix. And when it’s time to have my All-Time American Icons Barbecue, I’m inviting both Dwight Eisenhower and Howard Zinn. But I might seat them at different tables.

I am fascinated by American history. Growing up only a short distance from where the Mayflower arrived in 1620 might have something to do with it. So did being a Gen X child of the 70s, consuming vast quantities of Schoolhouse Rock along with my Froot Loops.

But mostly it was due to having some absolute rock star history teachers in high school and college. My 10th grade teacher gave everyone in the class bullets he’d collected from the ground at Gettysburg. Talk about keeping it real. Holding that amazingly heavy lead slug, helps me understand in a visceral way the price paid for that “new birth of freedom.”

By the way, if you ever find yourself at a friendly neighborhood flag burning, here’s a word of advice: bring a gas mask. Having attended a flag “retirement” ceremony last Memorial Day, I can tell you that a pile of burning freedom smells like a blazing truck tire stuffed with anchovies. Old Glory won’t go down without a fight.

And speaking of Old Glory, let’s finally get to the reason for this post. Namely, what the Stars and Stripes can teach us about reproducing color. Yes, it’s patriotic prepress.

One of my Three Cardinal Rules of color correcting is to make sure you get “known” colors right. The other two are neutralizing grays, and minding the shadows and highlights. (A lesser-known fourth rule is “never get involved in a land war in Asia.”)

We all have a set of memorized colors that comes from seeing certain things over and over. We don’t know the ink numbers, but we know what some things are supposed to look like. It could be something from nature, like a blue sky, or something from the supermarket, like a Coke can. If you’re trying to reproduce them for print work, they can look very wrong if you don’t go by the numbers and apply some accepted formulas, and account for dot gain (we’ll get to the evils of dot gain in a minute).

In the case of the Coke can, we can go to the Coke branding website and learn that Coke Red is L50 A71 B48. You won’t find a much redder red in the SWOP gamut (4c99m94y1k). In the case of the blue sky, there’s no exact formula, but you know it’s not supposed to be cyan or purple or blue-green. For a bright blue sky, my rule of thumb is twice as much cyan as magenta. So your daytime sky gradient goes like this:

Add M and then K with increasing velocity to bring on the night.

In terms of color, the American flag is made of blue sky and Coke cans. There’s something poetic about that, but I can’t quite grasp it. Where’s Walt Whitman when you heed him? More accurately, the flag’s red and blue are recognized standards: Pantone Old Glory Red (193) and Old Glory Blue (281). The current standards body in charge of these colors is known simply as The Color Association.

The flag’s white stripes are supposed to be neutral, not any kind of creamy color.
Last night, I made a set of swatches on kuler.adobe.com with these values and some darker shades to share with color-managed patriots everywhere. The base red and blue look very washed out on the kuler site, but once you load the swatches into InDesign or Illustrator, they look right.

Those values are your weapons in the fight for All-American color, but will they be enough? Think back to our house painting adventure. You can use the same LAB curves techniques to nail the exact values for the flag. Unfortunately, that alone won’t get you the right color for print because both the red and the blue are susceptible to an un-American amount of dot gain. And to make matters worse, Old Glory Blue is out of SWOP gamut. So is our dream of righteous color over?

“Over? Was it over when the Germans bombed Pearl Harbor?”

-John Blutarsky

Hell no! So what do you do? You learn about dot gain.

Dot gain is the darkening of colors in print caused by the spreading of ink droplets as they are absorbed into paper. In halftone screens, the larger the dot, the darker the apparent color. So when dots spread, it looks like more ink was applied. Dot gain doesn’t mess with your highlights or shadows much since those dots are too small or too big (i.e. nearly touching) already. Instead, dot gain affects the midtones most. In our flag colors, the midtone colors are the Y in Old Glory Red and M in Old Glory Blue. Dot gain in yellow isn’t that scary since it’s such a weak ink. But we have a big problem with that magenta. And I’ve seen plenty of purplish flags and skies in print to know that most people don’t deal with that problem.

We start by taking either a picture of a flag that is correct or has been corrected with the LAB technique, or a couple swatches of Old Glory Red and Blue in RGB. The next step is to adjust our Photoshop Color Settings. First, change the CMYK working space from SWOP v2 to Custom CMYK. The Separation Options let us replace cyan, magenta, and yellow, with black ink. By doing so, we can reduce the purplish hue while keeping the blue as dark as it should be. The default of Medium GCR gives us an out of gamut blue with 81m and 22y. No thanks. Light GCR, often recommended for offset printing gives us 84m and 25y, even worse. But UCR gives us 74% magenta and 10% yellow.

I think we have a winner. Here’s the magenta and yellow from UCR (top) and light CGR (bottom). If you were trying to avoid purple, which would you add to your cyan?

We’re halfway done. The other thing we need to do in this dialog box is to address the dot gain directly. Switch the Dot Gain setting from Standard to Curves. Now we need to drag the middle of the magenta curve up a bit.

This tells Photoshop how much dot gain we’re expecting on press, so when we convert to CMYK, Photoshop will remove magenta from the image to compensate. I moved cyan down a bit to 70, magenta up to 74, yellow to 68 and black to 74. Why? To leave more cyan, remove more magenta, leave more yellow, and remove more black.

Finally, let’s go ahead and convert to CMYK. And…we did it! The blue is 96c 69m 10y 30k (top). Even with some dot gain, that is going to be blue and not purple. The SWOP v2 default separation settings were going to give us and out of gamut 100c 88m 28y 28k (bottom). Keep in mind what you see here is going to purple up on press when those magenta dots hit the paper, making our UCR, dot gain curved blue, true blue.

When you’re done celebrating, put down the hot dogs and sparklers and go back to your Color Settings. For everyday purposes, restore them to light or medium CGR. You can keep the dot gain settings, but maybe move the magenta down to 70. Only one thing left to say, and the founding fathers said it best:

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