When taking your piece of digital design to the printed world, there is this nasty, some would say: evil, thing called CMYK. Dynamic Graphics magazine has a five-point article on how to survive in a CMYK world. http://www.dynamicgraphics.com/dgm/Article/28597
Excellent read, and even better: tag/bookmark it for later.
Some notes of my own, based on 8 years of questions from customers. I’ll add to this, so you can tag it and come back.
- In a majority of cases, a Print designer works in RGB or CMYK. RGB stands for Red-Green-Blue; this is ‘subtractive’ colors using light to generate the colors you see on screen. CMYK is Cyan Magenta Yellow and Black(K). This is a ‘additive’ mechanism where these inks are mixed together to generate the colors we see. Light is ‘reflected’ through the ink, off the paper to your eye. As these color mechanisms are very different, the color results are different.
- The screen; LCD or CRT, will not show all the colours that can be printed: especially in the shadows, blues, purples and oranges. CMYK has a color space that is different to monitors we view our designs. You can purchase devices to ensure that where colors can be displayed onscreen: they match.
- Set the background/desktop of your OS to neutral gray, and run the color calibration software to set your monitor correctly. The environment in which you evaluate color; the lighting, background lighting and the colors on your screen get in the way of color evaluation. If you can afford it, purchase a screen color calibration device. If you can print a neutral gray with no color cast (too much CMY), you are 80% to a calibrated device.
- Another “name” for CMYK is Process Colors, or just Process. Another way to think of this is “Process” equals “The normal Process”. All JPEGs may not be RGB; you can have CMYK JPEGs.
- There is a myriad of software components that can convert RGB to CMYK. These are called Color Management “Engines”. It is a mathematical process. Adobe Photoshop converts between these colorspaces. So does Apple’s Colorsync, so does the software that sits inside a RIP or a printer driver. As each of these pieces of software are not written by the same people, your results may and probably will differ depending on the environment. Use the software you can trust.
- Color Profiles, which describe the colorspace a particular image is “in” can be small, or large (up to 1Mb). Software as described above may use this Profile to convert from one colorspace to another; some software may ignore some parts of the profile and the color results will differ. Some printer drivers just use their inbuilt software and ignore the color profiles altogether. Color Management, to work consistently, needs to use the same “color engine” consistently at all points to be 100% perfect.
- Color Profiles describe colors in RGB, CMYK or a colorspace called “CIE L*a*b” (shortened to LAB). LAB describes color in a device independent (that is, not screen, not printer) using Lightness (L), Red-Green (a) and Yellow-Blue (b). If you use a Color Management Engine to convert from RGB to CMYK, the engine will pass through LAB first. Some specific colors, or color ranges, may have special “transforms” as described by the color profile.
- The CMYK colorspace can print a wide variety of colors. Look at a coffee table book; it’s is a high screen (150lpi to 175lpi) print – printed in CMYK. Yes, there are other color spaces that add 2 or more plates that “mix together” extra colors to result in a higher number of printed colors (also known as higher range colorspace). Printing CMYK + spot plates is not the same. The extra 2 plates are printing two specific colors. You are asking the Printer to add an extra two colors in the print run, add extra inks. This costs money. In a large number of cases, you are printing normal CMYK. Ensure your Spots are converted to Process (CMYK)
- Convert to CMYK as late as possible in your design, if you can. Keeping originals in a format closest to the original (RGB for Stock Photography, in the most lossless compression, or Camera Raw formats such as DNG) will mean that you can convert to the target CMYK and keep as much color in the pixels as possible. RGB, based on the same compression settings, will be 25% smaller, too.
- There is nothing like a printed proof from a color-matched, calibrated device. Inkjet or otherwise; to ensure a match. But also note that a proofer is not the press/digital press – so your design colors may not exactly match. If the proofer is not yours, ask when it was last calibrated. Ask if the paper and inks being used are consistent.
- Swatches from Pantone and others ensure that key colors: such as Corporate logos, match at print time. The colors on screen may not exactly match (see #1 above). Once you use these swatches, you are manually color managing. Pantone swatches have an associated CMYK value attached to the named swatch. Rarely will you use a Pantone color for a “spot” or extra plate.
- Once you “hard code” a CMYK value, or use a commercial swatch set like Pantone – you are in control of the color. Color Management may change the colors later on, but generally you are telling the Press operator: I want this mix across my four plates.
- If you work in RGB you are leaving other systems (ColorSync on MacOS X, maybe printing from InDesign) to decide how to convert to CMYK. If you are printing from Word to a consumer inkjet printer, the drivers are using RGB and the printer driver converts to CMYK (or more inks) for you. The more information you attach to your RGB image (source Color Profile for instance), the greater chance your output driver will successfully print the colors.
- Press operators are the most highly experienced color people you will ever meet. If you are at the design end of the world, and you meet one; buy them a beer or coffee and have a chat. Each one will have a story about an “unprintable job”. Given no proof, they will match the print to what our eyes will notice most: flesh tones, green grass/trees and a blue sky. The central modus operandi is to ensure that the color is believable in the printed result. Our mind is trained to recognise these colors based on our mental perception of the image as a whole. If there is a printed proof, they will obviously match to the proof. Trust the Press operator.
- RIPs, the devices that take your PDF or file and generate proofs or plates, rasterize (convert to very, very high DPIs) images (bitmaps) and vectors (text, lines, boxes) through different paths. Whilst there are settings in the RIPs to turn this off, you cannot be sure that this is the setting used. Be very, very careful if you are attempting to match the color of a vector object to the color in a bitmap object. RIPs may use their own Color Management Engine; generally this engine will be unknown to you.
References and further Reading
- Color Articles from Color Remedies. Greater than 6 years old, but still relevant.