Troubleshooting Color: Source Color Space

More than once I have been asked: "OK, so the color is wrong, how do I make it right?"

Troubleshooting CMYK color can be a pain, because there are often many places the problem could be lurking, and changes made in one, may inadvertently alter the output based on info from another. So in this five part series, we will look at five important steps to troubleshooting a color managed system, or colorimetric tuning.

As you all know, a color management system is usually broken into five parts:

1. Source color space
2. Media parameter setup
3. Source color space designation
4. Output color profile
5. Output calibration set

Part 1 - Source Color Space

Color files set up to be printed always use a color space, even when the exact color space is not known by the customer. In general, the source color space is either RGB or CMYK, and composed pages are often found to contain both. For most customers, RGB is preferred, since it offers a larger color gamut, and higher saturation levels.

RGB usually comes in one of two flavors: sRBG or AdobeRGB. The key difference is in the size of the gamut, with sRGB having a smaller gamut than AdobeRGB.

Any work produced on a Windows device will usually be in sRGB by default. RGB is usually preferred since most sources (scanners and digital cameras) generate RGB, and most display screens use RGB as a native representation.

Some customers use CMYK as a source color space, with many flavors possible; SWOP, GRACol, ISO, etc., each with multiple variants. (See the Definitions page for definitions of these and other terms) The CMYK color spaces are usually characterized by the achievable gamut of a certain printing technology (ink and press type) on a certain class of media. While designing in RGB offers more possibilities, designing in CMYK often assures the final output will be within gamut.

The CMYK source space may also be used to emulate the lowest common denominator of two or more digital printers/copiers when matching output between the multiple printers/copiers. 

In any case, the source color space and variant must be known for optimum output color. 

A tag or profile is frequently embedded into the source file to identify the color space being used. The tag may be directly read in the RIP's job parameters.  Embedded profiles, if present, should ALWAYS be honored.

If the source color space is not known or discernable, experimentation must be used to find the closest match.

Other parameters specified in the Source area of the RIP job setup pertaining to color are:

• Almost always leave at the Full Output GCR default, allowing GCR parameters in the output ICC profile to specify black channel generation. Setting this parameter to Full Source GCR5 may cause color translation problems and should be avoided.
• Rendering Intent : Usually set to Relative Colorimetric which assures maximum colorimetric accuracy of in‐gamut colors. The default Presentation designation increases chroma of many in‐gamut colors, often rendering them inaccurate. 
• Photographic (Perceptual) also changes many in‐gamut colors, but may be useful if the shadows tend to block‐up.

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Do you have a color management question, horror story or event to share?

Email me at reilley4color@gmail.com

Munsell Hue Circle

“Popular color names are incongruous, irrational, and often ludicrous.” – Albert Munsell

This is from the opening of Munsell's own color blog, which defines the Hue Circle.

Hue is the quality by which we distinguish one color from another, as a red from a yellow, a green from a blue. In science it can be measured and identified by its position within the visible spectrum. It is one of the three components that computers use to define color: hue, saturation, & value (chroma).

On the Munsell Hue circle, there are 5 Principal hues: Red (R), Yellow (Y), Green (G), Blue (B), Purple (P) and 5 Intermediate hues: Yellow-Red (YR), Green-Yellow (GY), Blue-Green (BG), Purple-Blue (PB), Red-Purple (RP).

When a color is void of hue it is called a Neutral, such as Neutral Gray or Neutral Black. On the Munsell Hue circle it is an axis in the middle (N).

Each of the 10 Hues (both principal + intermediate) are then further subdivided into 10. As you move clockwise around the circle the 5 of each Hue is the principal center of that color family, while the 10 of each Hue is considered the intermediate. Even finer distinctions can be made between similar Hues through the use of decimals.

The Munsell Color Order System is a way of precisely specifying colors and showing the relationships among color based on a three-dimensional model.

The primary hues in the RGB or CMYK models are shown around the Munsell Hue circle to show how they relate to the Munsell Principal and Intermediate colors.

RGB & Hue
Red, Green, and Blue are the primary colors for this additive color model in which red, green, and blue light are added together in various ways to reproduce a broad array of colors. Equal amounts of RGB = White.

CMY(K) & Hue
Cyan, Magenta, Yellow, and Black are the primary colors used in printing for full-color documents. Mixing varied percentages of of these four inks reproduce colors. Equal amounts of CMY minus Black (K) = Dark Brown.

A Munsell Notation is always written in a specific order as a fraction.

For example: 5R 5/5

5R = Red HUE at step 5

5/ = a VALUE step of 5

/5 = a CHROMA step of 5

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Do you have a color management question, horror story or event to share?

Email me at reilley4color@gmail.com

Tips for Great Color

Tips on Producing Great Color

Good color starts by calibrating all of the devices within the color work flow.
Devices should be calibrated often to ensure that they have not “drifted.” The frequency depends upon your reliance on color. As you know from reading this blog, calibrating brings the device to a known, stable state, and is a baseline.

Calibrating your monitor is just as important as calibrating the print device.
Whatever color space you might be working in, unless your monitor presents you with controlled, managed color, what you see will not match what you get. First, it’s important to think about the problem correctly. The goal isn’t to match the prints to the monitor or the converse. The goal is to make sure both the monitor and the prints reflect, as accurately as possible, the information that is actually in the digital file. There are lots of methods for calibrating your monitor, and it can get quite involved.

Here is a video showing how YOU can calibrate your monitor for FREE.

The major manufacturers of monitor calibration packages for the casual user are Datacolor (the Spyder series ), X-Rite (the i1 series, PANTONE Huey and the ColorMunki) and Integrated Color (ColorEyes Display Pro). All these products are of excellent quality. The first two have several price levels of packages with varying capabilities.

The more expensive packages may include features you don’t need, such as printer profiling and projector calibration, and the ability to customize calibration settings beyond the defaults. The accepted standard is to calibrate to a color temperature of 6500K, a gamma of 2.2 (for both PC and Mac platforms) and a luminance of 90 cd/m2 and these will be the default setting in all the packages. But some of the less expensive packages may not do everything you need, such as luminance adjustment. Check the details.

Some laptop screens may not be able to be calibrated properly, and older or very inexpensive computers may not be able to use a profile. Apple laptops will need the ColorEyes software mentioned above.

An issue with Windows is a utility called Adobe Gamma. If it is in your Startup file it will be loaded on startup and override your calibration settings. Simply go to Start > Programs > Startup, right click the Adobe Gamma Loader and click Delete. (If it’s not there, don’t be concerned.) Don’t be nervous about doing this. It only turns it off as a startup item; it does nothing to what is installed your computer.

A custom ICC profile should be created for each device within the Color Supply Chain.
This process ensures accurate and automatic translation of color values from one device to another, minimizing time and waste during the production process. A Device Link Profile can be established to link devices commonly used in the production process, eliminating the need to specify individual device profiles each time.

Paper, inks and toner impact the ultimate color result. Creating individual device profiles for each paper type, ink and/or toner used delivers a more consistent result. For example, if a proof is being generated on a glossy, coated stock, but the final product is being produced on a matte uncoated stock, these custom profiles can produce a more consistent result.

Spot colors can add time and cost to a printed project. Not all spot colors can be faithfully reproduced with CMYK four-color process. Designers and printers should carefully consider the colors that they are using within the context of the project’s budget and desired outcomes. Many tools exist that can help users determine whether or not a special color can be faithfully reproduced using a CMYK match. It is often necessary to use spot colors to consistently match special corporate colors and to ensure absolute color consistency across a distributed printing process.

Make sure you aren't "duplicating" any colors. 

Look through the color palette in your page layout software. Remove any duplicate colors you find, and reassign the corresponding objects and layers accordingly.

Make sure you give your colors the same names in each application you use for the project. 

For example, make sure you give the color the same name in InDesign as you give it in Photoshop and Illustrator. This will help reduce confusion and ensure the colors separate properly when preparing the piece for print.

Communication among all constituents in the color work flow is essential. This communication should include sharing of ICC profiles, discussion about paper and ink types and proofing models, and more. In doing so, good, consistent color can be produced across widely varying geographies and output technology types.

Using a good RIP in the production process is a critical element in the color work flow. It alleviates many color issues and reduces training challenges. Consistency in settings within the RIP is key to delivering repeatable and known color.

When using digital cameras or scanners for input, if you want your colors to be consistent from shot to shot, or scan to scan, include a color target in the first frame/scan of a sequence. When it comes to processing, set the grey point (and black and white points) using the target reference frame, and your software will match the subsequent batch of images.

Always color correct images in the largest RGB color space available. When images are converted from RGB to CMYK, you lose color information—a lot of it. As a result, you (and your color management tools) have fewer colors to work with, or average, when attempting to make color changes to an image. Also, when images are converted from RGB to CMYK, you’re creating the black separation and reducing the amount of CMY in the image at the same time. Depending upon how much CMY is eliminated in the separation, it can be very difficult—or even impossible—to make color adjustments to an image.

When designing for color output, avoid large solids. While lithographic presses have the ability to reproduce solids evenly, toner-based devices have a tendency to mottle, show unevenness, or even banding. This is because ink and toner are radically different materials. When toner is applied to paper, it is dry. Toner is not actually absorbed into the paper fibers, instead, it is fused to the sheet using both heat and fuser oil, creating a bond. Consistency lies in how evenly the toner was applied to the paper, and how evenly it was fused to the paper.

If tints and large solids must be used in a design, there are some ways to help counteract the uneven appearance associated with toner-based devices. First, try applying a filter (Photoshop Add Noise or Texture filters work well) to the large tint or solids. Another option is to also break up large color areas with other design elements such as text, images, or illustrations.

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Do you have a color management question, horror story or event to share?
Email me at reilley4color@gmail.com

Spot Colors

SPOT COLORS

Sometimes inks or toners are specially mixed to deliver an exact match to a specific color, rather than using CMYK inks to produce four-color process. In the offset world, ink comes pre-mixed in cans.

These special colors are called spot colors, or sometimes, Pantone colors. Pantone, Inc. developed the first color matching system in 1963. This proprietary system, called the Pantone Matching System (PMS), contains the formulas for creating and reproducing more than a thousand different “spot” colors on a CMYK device. This reason is why spot colors are sometimes referred to as PMS colors. Other color matching systems include HKS, Toyo and RAL.

It may be best to think of the Pantone library as a way to reference color, so that a person on the East coast can be reasonably sure that their printer on the West coast knows know what color they expect to see in the proof. If your Pantone swatch book is more than a couple of years old, it may not be reproducing colors correctly due to age, UV light damage, moisture, and other reasons.

In 2007, Pantone announced a new color matching system, called Goe, which consists of more than 2,000 colors. While there is some overlap between PMS and Goe, Goe does introduce a large number of new colors to the market.

If CMYK inks can be combined to create colors in a subtractive color system, you might wonder why there is a need for special spot colors. There are three key reasons special inks are used:

First, not all colors can be matched using CMYK, so they require a special spot color ink.
Secondly, it can be difficult to accurately reproduce certain color gamuts, such as saturated color. Finally, color shifts caused by mis-registration and process tolerance can occur when attempting to match a special color with CMYK inks. 

Spot colors can also be used for varnish effects, die cutting, or special effects in 5-color presses.

If the piece being printed is a full-color piece, additional spot color requires an extra printing unit on the press, or an extra pass through the press to create what would be five-color printing. That is, a four-color press has four printing units, each imaging one ink color (CMYK). To add a spot color, a fifth unit (or a five-color press) is required. Otherwise, the piece must be run through the press again to overlay the spot color. 

For offset printing, another pass through the press requires drying time (to let the first four colors dry), and complete wash-up of at least one printing unit to allow the addition of the special color. It also introduces the need to assure precise registration of the color being laid down in the second pass as it relates to the four colors that have already been printed. This process can add significant time and cost to a printing job.

For digital printers, which generally print using CMYK toner or inks, spot colors can be effectively matched using sophisticated algorithms within the RIP, which helps users manage spot colors and edit the CMYK or RGB values to better match corporate or custom colors. Even so, there are still some colors which are difficult, or even impossible, to match in the CMYK space.

When designing a printed piece, careful consideration should be given to whether or not a spot color should be specified. Quality, color accuracy, cost and the color-critical nature of the piece represent a few of these considerations. 

In some cases, it makes sense to use an alternative color that is more likely to reproduce accurately with CMYK inks. Pantone PMS and Goe systems provide Bridge Books as well as online software that help designers and printers determine how faithfully a PMS or Goe color can be reproduced, making suggestions about alternative color choices.

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PANTONE®, Goe™ and other Pantone, Inc. trademarks are the property of Pantone, Inc.

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Do you have a color management question, horror story or event to share?
Email me at reilley4color@gmail.com

Color Space

Color Space

In most cases, device-independent color definitions have three dimensions, and these dimensions make up what we call a color space. The dimensions are:

Hue: According to the American Heritage Dictionary, hue refers to a particular gradation of color such as a shade or tint, like “all the hues of the rainbow.” An individual frequency in the color spectrum. Humans are capable of discerning over 10 MILLION colors.

Saturation: This term refers to the vividness of hue or purity of a color. Intensity can be increased or decreased to suit.

Brightness or Luminance: (also called Value) The terms refer to the dimension of a color that can range from very dim (dark) to very bright (dazzling). A grayscale image is an example of an image represented with only the Luminance value.

Conventional four-color offset printing and most color digital printers use four colors – Cyan, Magenta, Yellow and Black – as subtractive primary colors to create a wide range of additional colors in what is known as four-color process. These four colors, referred to as CMYK, with “K” representing black, have long been the primary color space utilized in the world of printing. As mentioned earlier, CMY are the three primary subtractive colors, and when mixed in equal parts, in theory result in black. In reality, a dark color that is not a true black may result from less than ideal colorants, or impurities in the toner or ink components.

To economize on ink consumption and to produce deeper black tones, unsaturated and dark colors are produced by substituting black ink for the combination of cyan, magenta and yellow.

When an image is captured or created digitally — that is, scanned and captured with a digital camera, or created using desktop publishing software — it is commonly represented using red, green and blue (RGB) as this is the color language that your computer monitor requires. These colors are the additive primary colors that are mixed with light and used in displaying images on a screen. Here is a great video that shows you how to use this info to ensure your color palette will always harmonize when designing.

CMYK and RGB represent two very different color spaces. With the world’s increasing volume of digitally captured files, most of which are in RGB format, printers preparing a file for print must consider the color space in which various elements are created. Having the processes in place to convert these files as appropriate for the intended output device is equally important. To convert values obtained from an input device, such as RGB from a scanner or digital camera, into the device code values needed by an output (rendering) device, such as a CMYK printer, a transformation is needed to modify the data.

This role belongs to the ICC profile, which directs the actual color conversion produced by a color management module (CMM). The CMM uses the profiles to convert and match colors on one device’s color space to or from another device’s color space. When colors on one device’s gamut are displayed on a device with a different color gamut, the CMM attempts to minimize the perceived differences in the displayed colors between the two devices.

In general, you want to use color spaces that are as large as is practical. For example, if your printer is capable of producing output in a color space larger than sRGB, there is no reason to hobble your work by limiting output to the small sRGB gamut. If you do, you'll lose the saturated cyans and greens that can make your prints stand out.

Your applications and devices need to know what color space they are working with.

This most definitely includes your monitor. Without knowing what color space your monitor displays images in, it is impossible to accurately gauge how your images will appear in print. Calibration and profiling of your monitor is the first step towards a color managed workflow.

Most printers and all but a very few scanners or cameras either print or capture images in well-defined color spaces.

Larger color spaces contain both more colors and brighter, more saturated colors.

If your camera or scanner supports it, use a larger color space such as Adobe RGB.

Use sRGB for web graphics. This is at least in the same ballpark as most monitors. Using Adobe RGB for web images leads to washed-out looking colors in applications that are not color aware (i.e. most web browsers).

Your computer handles color differently than your monitor does, and differently than your print output requires. Your computer understands color in LAB colorspace, which we will discuss in detail later. The CMM translates from RGB to LAB and then from LAB to CMYK based upon ICC profiles. This interim colorspace is called Profile Connections Space (PCS) is either CIELAB (L*a*b*) or CIEXYZ.

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Do you have a color management question, horror story or event to share?

Email me at reilley4color@gmail.com