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RGB & CMYK +
PMS = Color Confusion What is the difference
between RGB and CMYK Color environments and how does each function?
Includes a sidebar on PMS (Spot) colors. If you’ve
been around designers or printers at all, you’ve likely heard
conversation around CMYK, RGB and PMS. At some point it may have piqued
your interest but perhaps you didn’t want to ask. Especially about
that PMS one. "What ARE you folks talking about?” you
probably thought. Well, here’s my attempt at explaining complex color
theories in common terms. This is an overview and won’t get into the
truly technical realm. “CMYK”,
“RGB” Each of these acronyms refers to a method of building colors
for different environments. RGB The one that
you are perhaps most familiar with (or aware of) is RGB. If you are
reading this, you are reading an RGB display via your computer. RGB
stands for Red, Green and Blue. The three colors that create every other
tone of color that is visible on your screen. There is no black or white
‘color’. Neither is there yellow or purple. They are all
combinations of red, green and blue. White is the sum of all three
colors while black is the absence of all three colors. Here is a small
swatch with a bright blue and its RGB color formula:
While each
monitor is capable of displaying a wide range of colors, there are still
inconsistencies between computers. However, these are often noticeable
only to those in the ‘know’. On more than one occasion I’ve gone
to friends houses only to be dismayed at how different things can look
from machine to machine. These friends are common consumers and I took a
look at their system settings (default) and they were only running at
hundreds of colors, rather than thousands or millions. I encourage you
to check your settings and perhaps see what you’ve been missing by
moving those settings up a notch. I expect that my fellow designers
would see something much more close to what I’ve got on my display. I
don’t assume that it’s the same, just closer. This very problem, er
– challenge, led to “Websafe” colors. That fantastic range of
merely 216 colors that web designers have been stuck with. Fortunately
today that limitation is certainly the lowest common denominator and you
can get away with an expanded palette in most circumstances.
Websafe colors
are referenced by their hexadecimal number. These color’s names are
pairs of characters, e.g. FFCC00 and OOCCFF
are colors you can specify and expect them to render fairly consistently
from one machine to the next. All colors have a hex name/number but they
may not reproduce properly on low-end or older systems. CMYK If
you were reading this piece in a printed magazine, you would be reading
it in a CMYK color space. CMYK color space is all around us, you can’t
escape it, it has been around forever and is more pervasive than RGB but
much less understood. I’ve
met a number of web designers and even illustrators who don’t
understand the difference and theory behind CMYK vs. RGB. As
opposed to RGB which builds color through the addition of light, CMYK
adds color through the addition of colors. Because of this, colors
reproduced in CMYK sometimes can ‘t match colors created in RGB. For
example, if you open up Photoshop and create a CMYK image, when you go
to your color picker, certain colors built with non-CMYK color will be
displayed with an alert, notifying you that the color can not be
re-created with CMYK. Photoshop gives you the courtesy of showing you
what the CMYK equivalent will look like.
If
you look to the left of the ‘Cancel’ button you will see an alert
symbol. This tiny thumbnail shows you the CMYK equivalent of the color
you’ve chosen. The tiny cube below that and next to the ‘Custom’
button is the closest websafe color to your color formula. These are
very useful indicators when choosing colors that may be critical to your
design in multiple mediums. This
is the closest CMYK equivalent to our Blue Swatch above.
You
will notice that the blue shifted slightly and looks less vibrant. This
is because the CMYK color formula has a smaller range of colors than RGB.
Pictured below is the color picker that I used to shift this RGB blue
(51, 51, 187) to CMYK (88, 85, 0, 0). Note that because I changed it to
a CMYK color, Photoshop also adjusted the RGB values to 65, 72, 158).
The two swatches shown in the image (on the right) show your current
color selection on top, and the last beneath it. This is extremely
useful when creating original artwork or retouching images in Photoshop.
Comment - If you’re wondering where HSB fit into this, this is another way to pick colors and is closely related to RGB. Instead of specifying color mixtures, you select a hue (H) and then adjust its saturation (S) and brightness (B). This is my personal preference although you could select colors the same way by using RGB or LAB. In
four-color process (CMYK) printing, primary colors (Cyan, Magenta,
Yellow, and Black) are mixed together to produce most of the colors that
you see in normal magazines and color books. While there are six-color
color spaces, these are much less common and are used for specific
printing techniques. CYMK
is what the vast majority of commercial printers do, although there is a
wide range of options that we won’t get into. Images and artwork
targeted for reproduction in a CMYK color space must be properly
formulated to print correctly. If you’ve had the misfortune of trying
to get an accurate print from an RGB image, you’ve just had a glimpse
into the technical realm of 4CP (four color process) printing. To
further confuse the issue, printers will often refer to their presses as
4, 5, or 6 color presses. While this makes sense to print designers, it
is often lost on other customers. These numbers refer to the maximum
numbers of colors that can be run in a single pass. For example, a
tri-fold brochure could be designed to be printed in CMYK, plus a spot
varnish, plus a metallic spot color. This ‘job’ is known as a
six-color job since there are six colors of inks that will be run in a
single pass. Was that confusing enough? What about ‘spot’ colors… Spot
colors, also known as PMS colors, and officially as Pantone Matching
System colors. Are specific color formulas that will reproduce
accurately in print. Instead of simulating colors by combining primary
colors, spot (PMS) colors are pre-mixed with existing and published
color formulas. Because of this, you are nearly guaranteed that your PMS
186 from one printer will be matched by a PMS 186 from another printer.
Better yet, often these PMS colors are pre-mixed by the ink factory,
leaving even less to chance. “Spot” colors refer to the actual
printing process by which they are applied. It is possible to have spot
colors that actually have no color to them at all. Spot varnishes are
glossy or dull varnishes applied to specific areas in a printed piece to
achieve specific results. Spot colors may also be used in design
applications to indicate die-lines, embosses, foils and heat stamps. At
this point, if you already know what a foil and a heat stamp is,
you’ve got the jist of it and my aim is not to tell you something you
already know. If
you are really into colors and color combinations, pick up a book called
“Color Index” by Jim Krause, published by HOW Design Books, it is a
great (tidy) resource by which you can get inspiration and ideas.
Believe me, I buy a lot of books and this is a keeper. ©
2002 Matt Frederick (Originally
published in Applelust.com) Since then he has found a happy home at a growing software company where he designs a wide variety of media. In mid 2000, Matt started a freelance design business to supply a needed bit of variety in his design diet. In his spare time, Matt creates artwork and photography, which you can find at http://www.themirrorpool.com theMirrorpool. He is the founder of a digital collaboration group called digart209. http://www.digart209.org. Digart209 promotes collaboration between artists of different mediums and strives to build the local design community. To learn more about Matt's work and to see examples, check out these links: http://www.themirrorpool.com
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