GCR (Gray Component Replacement)

Experts agree that in color reproduction black can be beautiful if used wisely. Black can add details and contrast in the reproduction which is impossible to achieve with the three process colors. However, if the black is not used judiciously, it will do more harm than good. It will make the colors look dirty and create an unnatural contrast.

— Dr. R. K. Molla

Reseparating customer supplied files is rapidly gaing popularity with printers and publishers as a way to lower print manufacturing costs. Reseperating allows for greater control of the final output, including specific filtering for media, color management, and finishing options.

Although the application is not limited to specific print market segments - these are the ones that are most quickly adopting this technology:

• Newspaper publishers
• Insert and flyer printers
• Magazine publishers
• Catalogers
• Directory printers

Within the CMY color space, a range of colors can be achieved by combining the three primaries. This combination in its turn can be thought of as a hue component (which will require a maximum of two primary colors) and a grey component (a mixture of all three, in an appropriate quantity to give the required saturation). If the grey component is replaced by black ink, the same color is being achieved by using two primaries and black. The act of substituting a quantity of black for the grey component is known as "Grey Component Replacement" (GCR).

GCR is also termed "achromatic color removal."

In grey component replacement (GCR), contrary to under color removal (UCR), the CMY values that add to grey all along the tone scale can be replaced with black ink. UCR only adds black to the CMY equivalent of what would have printed as a grey or near-grey.

Although there are many benefits to reseparating customer supplied files in order to use GCR, the most promoted and fairly easy to justify is in regards to reduced ink usage - typically suggested as a savings of around 20% in CMY inks with an increase of about 6% in K ink used while maintaining the same visual appearance in presswork.

Based on that figure, calculating a return on investment seems fairly straight forward. For example - based on the industry average of ink consumption for a sheetfed printer being about 2% of their gross earnings, a $10 million dollar a year printer will spend $200,000 a year on ink. If they reduce their ink usage by 20% they will save about $40,000 a year in ink costs. Theoretically, if the printshop spent $10,000 on a reseparation solution their payback time would be just three months and they will have saved $30,000 in the first year of implementation - a very good investment.

This is the removal of the gray components of the three colors and replacing them with black.

In GCR reproduction, all the primary and secondary colors remain the same as the normal chromatic reproduction, however, the blackening effects by the tertiary colors along with the gray components of the other two colors are removed and replaced with black. 

Various percentages of GCR can be applied to the separation for economical reasons and visually more pleasing results. The black dot sizes are increased to replace the gray component that has been reduced in the process colors. If 100 percent GCR were used, every color area in the reproduction might contain dots of only black and two or three process color inks. 

Commonly used percentages are 50% to 75% GCR. The goal of GCR is more consistent color, increased detail in the shadows, shorter press makeready, and possible ink savings.

Advantage: GCR results in less ink being used, and some of that ink is black which is normally cheaper than the others.

Advantage: The areas where less ink is used are regions of high ink use, so the potential for drying and offset problems is reduced.

Advantage: The resulting output is less susceptible to changes in the printing variables since you are not continually trying to balance as much C, M, and Y.

Because a GCR separation uses a non-chromatic color – black – throughout the tonal range and reduces the proportion of C, M, and Y in the mid- and quarter tones, the color in GCR separated images is more stable as solid C, M, and Y ink densities naturally vary through a press run. Note, however, that the added stability means less ability for the press operator to move color if required. For many printers, the increased color stability is a perfect compliment to the industry trend for a “by the numbers” print manufacturing process.

Other advantages:

• Reduced make-ready times/faster start-ups/less wastage
• Harmonized separations enhance press form printability
• Reduced fan-out or web growth
• Dramatic improvement of image appearance when slight press misregistration occurs
• Reduced drying times
• Higher printing speeds
• Improved repeatability of print jobs
• Grey balance within images is more stable


Disadvantages of GCR include:

GCR may reduce the ability to adjust some colors.

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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