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Color Conversions from RGB to CMYK

Color Conversions from RGB to CMYK


I’d like to start with something of a disclaimer. Much of the work we do at Rise is in the digital realm. We strategize, design, and build primarily for the web. We will, however, have clients come to us needing a new business card designed or a logo redesigned or a mailer constructed. What all of those share in common is that they must be able to be seen, not just on a computer screen but printed out. And while we are diligent in making that translation from web to print, every once in a while the conversion is a little bumpy.

So, when that business card comes back looking red instead of magenta or dull blue instead of bright cobalt, what gives? Does the printer not know what they’re doing (assuming you use a professional printer)? Are your electronics scheming against you (sometimes I swear my computer gives me funny looks)? Are your eyes finally giving out on you?

Rest assured, none of these is likely the issue. More often than not, issues at the printer usually have to do with 2 things: the difference between the RGB palette belonging to computer screens and the CMYK palette at the printer and image resolution.

This is an early color photograph taken by Sergei Mikhailovich Prokudin-Gorskii as part of his work to document the Russian Empire. Three black-and-white photographs were taken through red, green and blue filters. The three resulting images were projected through similar filters. Combined on the projection screen, they created a full-color image. Source: Wikipedia
Empire_Stikes_Back

RGB vs. CMYK

When it comes to color on a computer screen and color via ink on paper at the printer, we must look at two very different ways of creating the colors our eyes see.

Let’s start with the way we see color on a computer screen. Computer screens (similar to TV screens) make colors using the RGB color generation method. RGB stands for red, green, and blue, the colors of light that are combined to create the “RGB palette”. These different colors of light are added together to create images from out of darkness. This type of color creation is also called additive color mixing because light must be emitted (or added) to produce a given color.

Moving onto subtractive color mixing, we find this sort of color model used when something is printed using ink. In the printing process there are 4 ink colors that work together to create all the colors able to be printed: Cyan, Magenta, Yellow, and black (CMYK). Colors made this way are called subtractive because the inks absorb (or subtract) all the colors in the visible light spectrum save the one they are meant to reflect, namely, any combination of the ink values in cyan, magenta, yellow, and black. To give an idea of what I mean, when yellow and cyan ink are printed onto a white sheet of paper, those inks absorb all other colors except green. All other colors are absorbed by the ink (subtracted) and green is reflected back to the human eye.

CMYKCYMK

The Issue(s)

So, when you take an image created on a computer screen that uses RGB color generation and forward it to a printer that  creates color through the use of CMYK inks you’ll usually notice a color shift that is less than ideal. The reason for this, in addition to switching from light-based color to ink-based color, is that the computer and printer are having to try and translate a three-color image to a four-color image.

The other issue comes from resolution. The same image that looks bright and focused onscreen prints with an edge that can only be described as fuzzy. This is because most images meant for a computer screen fall somewhere between 72 and 96 pixels per square inch, whereas printers begin at 300 pixels (or “print dots,”in simple terms) per square inch and range up to 1,200 pixels per square inch for a high end consumer-grade printer like the HP Color LaserJet CP2025dn.

The Lackluster Color Fix: Tips & Resources

While it is next to impossible to ever fully translate the color from your screen to the printer, there are a few tips that can make life - and the colors you want to present in your printed materials - a whole lot happier.

First, when creating your images, see if the editing software you’re using will allow you to switch from RGB to CMYK. Most will, but if for some reason it won’t, you can use the handy dandy converter at rgb2cmyk.org for free, in a pinch.

You’ll also want to make sure you are working with an image that has a high enough resolution to successfully render your work on paper.

Between switching to the proper color generation palette and double-checking your resolution, the headache of receiving printed materials that barely resemble your original color choices should be alleviated.

What do you think, COLOURlovers? Do you have any other tips for a successful screen-to-page transfiguration?  We’ve only touched on the basics here. We haven’t even begun to look at things like paper quality, paper color, and different kinds of consumer-grade printers (be on the lookout for future posts perhaps). If there are any printers out there, we’d love to hear how you approach the RGB-to-CMYK conversion issue - or anything else you might know more about in the print-world. :)

We look forward to hearing your ideas and sharing more of ours, wherever the conversation leads us.

Rise Above,
Stephan

CMYK_Tartan


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15 Comments
Showing 1 - 15 of 15 Comments
Shame that colour has to be so complicated when it is such a joy to use. Stunning blue garment in the above photograph. Would love to see it 'for real'
Here in Sweden there are a number of printers who are providing their own conversion specs for documents. They take into account paperstock, ink saturation and colour values. Was the first time I've encountered this kind of pre-press formatting - previously only packaging a document with InDesign and whizzing it off on a dvd. The folk I worked with this time though gave me a specific pre-press export setting to turn the doc into a PDF, adjusted to paper and inks. We did then have to upload the document to their system which then traced any saturation and overprint problems so you could alter images on the hop.
Was a very interesting approach - a little more labour intensive on the part of the client but produced a very good job - I think with my document they actually re-rastered the images to 250dpi instead of 300 which actually crisped them up!
From my position as a 'hack I would add that your point about the image size is very important and add that if folk are in the business of sending things off to journalists and magazines for consideration I would always make sure they are 300dpi and already in CMYK as you would be surprised how much an editorial team will love you for these two very simple things.
Great post Mr Barrett.
Team
@rdprime Great content and response. :) Thanks for all the input!
Team
going off what @rdprime said, I'd personally like to have a post on the that process of packaging a PDF with color profiles for printer specific items. It's kind of an interesting process and more heavily involved for things such as book printing, product package design... etc.
interesting! It got a little losty for me there, but i pressed on (Scrolled the mouse) and reached the end. ahha. My qn is that why is CMYK not CMYB instead if it's referring to black? And.. colours tend to come out yucky when printed.. :(
The K stands for 'key' - when the CM&Y plates on a press are keyed in/aligned against the black key plate.
I think you nailed the key points for color conversion between screen (RGB) and print (CMYK). Its so basic, but its not often understood. I'm not a printer, exactly, but I did work at the print shop at my art school for two years where we had a few EPSON inkjets and a Xerox Ducolor and the biggest complaint we got from students was that "the colors didn't come out right"....its because we don't print in RBG that's why!

I look forward to new articles relating to this topic. There is so much to talk about!
I would be interested to hear how color management is working for folks these days. I mainly work in RGB for the web and I've found that CM has come along way in ten years - fifteen years.

Are the CMYK profiles that you use working well? (Meaning, is soft proofing on a reasonably well calibrated monitor at least *somewhat* more accurate than it was a decade or so ago?)
@robtmann
CM has come a long way the in the last 15 years. We saw the evolution from Apple's Colorsync to ICC. We saw the introduction of the Colortron (a predecessor to the Colormunki). With the Colortron came affordable hardware calibration. Many print and design related companies implemented ICC compatible color management in their workflows. These days, most printers won't give you a blank stare anymore when you drop the term 'color profile'. Most, but not all...
In any case, CM can work very well, much better than most people expect. If you know what you're doing...
Very cool. I love the picture of that russian guy too :D
Isn't it true that RGB has more color in it than CMYK?
I always leave de CMYK to the printers. One of them has it's profile on there website with an instruction how to instal, how to convert and how to safe in a PDF.
Because I still think that the saving in PDF has a lot of options and I always forget how much (didn't find the right translation so I wright the long version) border you need to ad on the document.
I'm about to print a wallpaper for my brothers living room. I hope it turns out well! Has anyone experience in this matter?
postbacc wrote:
Very cool. I love the picture of that russian guy too :D


Haha, yes, that's a cool photo. It's interesting how they made that a color photo. Ahh how technology has changed the world.
liekejansbeken wrote:
Isn't it true that RGB has more color in it than CMYK?
I always leave de CMYK to the printers. One of them has it's profile on there website with an instruction how to instal, how to convert and how to safe in a PDF.
Because I still think that the saving in PDF has a lot of options and I always forget how much (didn't find the right translation so I wright the long version) border you need to ad on the document.
I'm about to print a wallpaper for my brothers living room. I hope it turns out well! Has anyone experience in this matter?


Yes, I do think the RGB color space has more values than the CMYK space. That's why certain colors on screen don't print well. As long as you stick with your printer's profiles, you should be in good shape :)

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