What the Heck is a Gamut?

Sup_Conversion_Sample

© DC Comics

You’ve just finished coloring this amazing Superman cover and couldn’t be more proud of your work. There’s Sup’s vibrant blue suit and his iconic bright red cape. Looks amazing on screen, right? You finished your work, saved it as a CMYK TIF and sent it off to your editor of approval and 15 minutes later your get a frantic email back saying the suit looks like mud and the cape is a weird, drab color and you may have to re-color the whole thing! Oh, and your deadline is 30 minutes from now. ZOIKS! What the heck happened!? It looked amazing while you were coloring it and now it looks terrible. Why did your colors get turned into mud? Because the colors you chose or created were outside the CMYK Gamut your computer converted them and the result was terrible.

I can see you staring blankly at the screen asking, “What the heck is a gamut?” Allow me to explain a little.

VisibleLightSpectrum

So let’s start this by talking a little bit about the science of color. What we perceive as color is our brains interpreting different wavelengths of light emanating from, or bouncing off of, objects in space. If we look at the color spectrum we see that long wavelengths appear as red warm colors while shorter wavelengths appears a blue, cooler colors. As those wavelengths get longer (moving to the left on the chart) we move into infrared colors, microwaves and various other electrical waves. As they get shorter (moving to the right on the chart) we get into Xrays, Gamma rays (our favorite!!) and other harmful radiations.

What we can actually see, however, is just a very small portion of that spectrum which we call visible light.

Visible Color Gamut

If we pull out that visible portion of light, simplify it and twist it into a circle we get every artists BFF, the color wheel.

But if we take that entire spectrum of visible light and twist is into a circle we see what is called the visible color gamut. Keep in mind…this example you see here isn’t ACTUALLY the full visible color gamut because you are looking at it on a computer screen which presents color to you in an RGB color space…but I’m getting ahead of myself.

RGB variation

 

This visible color gamut represents all variations of every visible color. So in this example the black arrow over the blue indicates every possible variation of the color blue. Very bright and intense colors exist at the outside edges of the circle while less intense, desaturated colors exist at the center. In order to make this a little easier for you to see, I’m going to replace our circle with one that has an exaggerated difference in saturation level from outside to the middle.

RGB Circle

So nature produces an innumerable amount of wavelengths of light, most of which we can’t see, but we create our artwork using technology that has yet to be able to reproduce all the colors of visible light. Specifically our computer monitors reproduce color in what is called the RGB Color space. This sort of bloated triangle shape over the visible color gamut indicates which colors are actually reproducible in the RGB Color Space. Using red, green and blue your monitor can recreate MOST of the colors in the visible light gamut, but not all. You’ll notice that it has trouble with some of the more vibrant orange, teals and violet colors. This is why your photos of those gorgeous sunsets never look quite right. Your camera is translating those natural lights into RGB and a little something gets lost.

CMYK Circle

However, when our artwork is complete it has to go to print. Modern printing presses mix 4 inks (Cyan, Yellow, Magenta and Black) to create “Full Color” your prints. As you can see the CMYK Color space is REALLY small compared to the RGB Color space and encompasses most of that drab, desaturated area in the middle of out circle.

CMYK-RGB Color Circle

You can really see the difference here when we lay the RGB and CMYK color spaces on the same graphic. By now you’re probably asking, “what does this mean to me, the comic book colorist?” MOST colorists, including those of you using the Hi-Fi method, render their work in RGB so while we’re working we have to always be aware that before each page is finalized it will have to be converted to CMYK.

When you color an image in RGB and the color you choose (or create inadvertently) falls outside of that CMYK color space it will have to be converted before it goes to press. Maybe I’ll cover how your computer makes those decisions (Relative Colorimetric vs Perceptual conversions) in a later article but suffice it to say your computer will select each pixel containing color outside the CMYK color gamut and changes it to a color that it thinks best represents the original color.

Just a note: I have again exaggerated the colors in the following example so you can better see the way the colors change.

conversion_rgb

Let’s take a look at your Superman from earlier and find out what happened. If we pull out the blue and red from the image and roughly plot them on the RGB color gamut you can see that they fall well outside of the CMYK gamut.

conversion_cmyk

When you convert that file from RGB to CMYK your computer decides what those new colors should be.

Now instead of those nice bright colors…they are muted and kind of dead.

Conversion_test_RGB

 

 

And if we look at them side-by-side you can really tell the difference in the color. So what can we learn from this exercise? First of all, when you’re coloring try to avoid selecting colors that are TOO vibrant and over-saturated. That’s your first clue that you may be heading down the path to conversion trouble later on.  Also, make sure you are using the View/Proof Colors option in Photoshop. That will allow you to color in RGB but have a CMYK preview on your screen while you work. You’ll immediately know if a color is going to end up looking gross.

At this point you’re probably asking, “Well why don’t we just skip this whole mess and color right in CMYK? Wouldn’t that avoid this whole problem in the first place?”

Well, yeah…but it leads to some other issues that are not as easy to overcome than coloring in RGB but being mindful of a future need to convert. We color in RGB because that is how Photoshop was intended to work. It was designed as a digital space for creating and editing images and digital space means RGB. Because of this in CMYK there are a LOT of tools that aren’t available to you at all. You will find that those tools that are available to you will give you a drab, gray-ish color when used in a CMYK color space instead of the rich, full colors you would get were you attempting the same process in RGB.

SizeCompare

Also, your files can be SIGNIFICANTLY larger. These two files are the EXACT same PSD except one is RGB and the other is CMYK. The CMYK file is almost twice the size. So, yes…you could avoid all the RGB to CMYK conversion problems entirely by coloring straight in CMYK but at a cost of lack of tools, lower functionality of some of Photoshop’s tools and potentially gargantuan file sizes.

Proof ColorsProTip: when coloring in RGB make sure you have the View/Proof Colors (Ctrl+Y) option active in Photoshop. This will allow you to color in RGB but see what the file will look like when it converts to CMYK. You’ll know instantly if a color you are creating is going to look like mud.

 

Eric White is a graphic designer and artist with 15 years of experience in the printing industry. He’s been working with Hi-Fi since 2008 as a consultant, web-guy, go-get-er, flatter and colorist. You can find more of his work at his website www.geekywhiteguy.com or follow along on twitter @Geekywhiteguy