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The Art and Science of Color Management for Sublimation

Posted: 28/06/2016 17:32 by Robin Kavanagh | with 0 comment(s)

Have you ever noticed that the color of an image on your computer screen never quite matches what comes out of the printer? Or the colors on a sublimated substrate may not match exactly with the colors your customer is expecting? These are all common issues that we in the sublimation industry have faced at one time or another. The term “what you see is what you get” certainly doesn’t apply here, and in reality, the whole affair can be quite frustrating when trying to create an image for sublimation or inkjet printing.

This is where some basic knowledge about the science of color and the art of generating the colors you need come into play. This article will introduce you to some basic concepts about managing color for sublimation printing and how you can use this information to reduce waste and print more economically.

Monitors vs. Printers

Though it would be nice to have an exact match between screen and print, it’s not a very realistic concept, as monitors and printers produce color using two totally different methods.

Computer monitors emit color as RGB (red, green, blue) light. Although all colors of the visible spectrum can be produced by merging red, green and blue light, monitors are capable of displaying only a limited gamut (range of color) of the visible spectrum.

Whereas monitors emit light, printed products absorb or reflect specific wavelengths of light. Cyan, magenta and yellow pigments or dyes serve as filters, subtracting varying degrees of red, green and blue from white light to produce a selective gamut of spectral colors.

Like monitors, printing inks also produce a color gamut that is only a subset of the visible spectrum, although the range is not the same for both. Consequently, the same artwork displayed on a computer monitor may not match that on a printed publication. 

These two diagrams show just how distinctly different the color spaces are. This also helps to explain the difficulty in accurately converting from one color space to another, as monitors are RGB and printer inks are CMYK (K stands for black).  Thus, every RGB image displayed on your computer has to go through a conversion process to CMYK before it reaches the printing stage.

Colors vary from monitor to monitor and from printer to printer. You see this all the time in electronics stores that sell televisions and computer screens. The variation in color output from screen to screen can be significant, depending on the manufacturer, type of visual output and setting. The color generated on the printed page is dependent on the color system used and the particular printer model, not by the colors shown on the monitor. Color correction is the art of adjusting this color transformation so that you can produce the best quality results on your substrate.

One of the most important considerations for sublimation color management is the selection of the printer and the inkset itself. Today, new sublimators can choose between the SG400 and SG800 for desktop printing, and the VJ 628 for wider printing. The SG printers are available in a four color (CMYK) configurations, while the VJ 628 is also available in an eight-color configuration.

It was once thought that only an eight-color printer could stand up to the level of color vibrancy and accuracy demanded by the likes of professional photographers. However with today’s inks and color management software, even the four-color desktop printers can yield stunning images.

Color Management Software

There are three basic types of software used for dye sublimation color management: ICC profiles, custom printer drivers and RIP software. Though each is somewhat similar, they have important differences, which we detail below. 

ICC Profiles

An ICC (International Color Consortium) profile is basically a set of data that ensures that when a specific color is selected on the computer screen, the designated color is consistently and correctly delivered on the substrate.  Think of it as a color-matching program, as the screen color rarely produces exactly the same output color. A profile creates a link between specific screen colors and specific output colors. It doesn’t change the color, rather it ensures the correct output for a given input.

To use this method, you must work with ICC compliant graphic software (e.g. Photoshop, Corel). The profile will be placed in the output stage of printing and the manufacturer’s (OEM) printer driver will be set to ‘No Color Adjustment’. This setup will color correct the image and then send the data to the printer without affecting the colors further.

Color correction profiles for dye sublimation have their own unique challenges however. Under normal profile creation, when a printer has printed out the color swatch for testing, the profiling software knows how to adjust the colors to print out the correct ones. When a dye sublimation transfer is pressed onto a substrate, the ink turns into a gas, and while in this state, the colors change properties.

This change can be quite dramatic (e.g. some blues look like green on paper), and it is, therefore, impossible to judge whether the print is correct or not until it is sublimated onto the final substrate. Thus, it is necessary to create custom sublimation profiles and print management application of these profiles to create the correct sublimated color, not the color on the printed transfer.

Custom Printer Drivers

Custom printer drivers are programs that have color correction built into the printer control system. The advantage of these programs is that color correction is performed at the printer driver stage, and they are generally easier and less technical to use an ICC profile.

 

Sawgrass offers the exclusive PowerDriver v4 printer driver system for most of its sublimation products. It contains built-in optimized profiles, optimized for the printer, inks, transfer papers and specific products. It should be noted that PowerDriver works with most popular graphics programs, including Adobe Photoshop, Illustrator and CorelDRAW, and Windows OS.

What is really great about PowerDriver is that you get the advanced color management capabilities of a RIP (see below), in a much easier-to-use program. Its settings allow you to choose specific papers, substrates, advanced color control for graphics or color / B&W photographic reproduction, as well as other variables to both streamline production and create optimal prints. With built-in utilities, resources and a multilingual user interface, including built-in help assist, PowerDriver v4 has been designed to make managing sublimation prints easy and efficient. 

PowerDriver also provides a color palette (ColorSure) for the graphics program so that a user can select pre-configured spot colors from the palette, while working on images, thereby ensuring that the correct “final” color will be consistently produced during the sublimation production process.

Whether using an ICC profile or a custom printer driver,  we suggest you create a color “chart” by printing out and sublimating the entire palette to a pure white your specific substrate. This creates a visual reference that you can refer to and show customers. Sawgrass’ ColorSure palette is included with PowerDriver, and those using an ICC profile can create a simple palette of their own to use.

The printed chart (see the image above) demonstrates the exact color that is created via sublimation (plus the RGB settings), so the graphic designer has an accurate reference when choosing the proper colors for the image being created.

Though the colors may not look the same on the screen as they do on the final substrate, by choosing the desired colors from the chart, you are assured that the output will be a match each and every time, regardless of what is “displayed” on the computer monitor.

Raster Image Processor (RIP)

More sophisticated users may choose to use Raster Image Processing (RIP) software, which includes ICC profile creation capabilities for managing colors. Simply put, RIPs convert images into individual dots (rasterizing) and sends these rasterized files to the printer.

The process of creating ICC profiles from scratch is time consuming, requires a good understanding of color science and is an art form in itself. It begins with printing a linearized color pallet. A spectrophotometer is then used to measure the colors. From these data points, the software creates an algorithm that calculates the color space and generates the ICC profile. Various types of images are then printed on a variety of substrates, and the profile is meticulously adjusted to optimize the final result.

RIP software also handles workflow tasks, such as nesting images and batching or queuing files to print. RIPs are available from a number of software companies, including Wasatch and Ergosoft. Sawgrass recommends the use of Wasatch SoftRIP with the VJ 628 for users looking for a more sophisticated color management and production solution.

Defining Color Space

No matter which color management solution you choose to work with, once critical step is defining the correct color space or mode within your graphic design software. These programs enable you to use different color profiles. When working with sublimation, you need to activate a specific RGB profile in order to produce accurate colors, unless working with a RIP, which uses CMYK.

Designs and images often come with their own embedded profile. When opening in your graphics program, you’ll need to make sure it is converted to the appropriate sublimation profile. For example, many of graphic artists design in CMYK color mode because this is the most appropriate for commercial printing. Because sublimation requires RGB, these files need to be converted upon importing in to your design software. The reason for this is that sublimation profiles are built to convert RGB colors to CMYK output, not CMYK to CMYK (unless using a RIP, which works CMYK to CMYK). If you try to print a file that is CMYK, the conversion will not work correctly and the colors will be off.

​For example, a Virtuoso customer recently contacted Sawgrass Support because the colors on his coaster prints were not coming out correctly, even though he was using PowerDriver v4 to manage output through CorelDRAW. He had noted that he had no trouble when printing an RGB image, but that CMYK images were printing all wrong. We asked him to check what his version of CorelDRAW had set as the Primary Color Mode. He found that it was set for CMYK. Once he changed this setting to RGB, he was able to get prints with the deeper color he was expecting.    

Be sure to check with our Technical Support Team for instructions to ensure you have the correct settings for your specific graphics program, and that you’ve installed your color management software correctly. 

To sum it all up, the simplest and most-important rule for color management in sublimation printing is consistency. Any change in a variety of variables will impact the final output. These include substrates, sublimation paper selection, pressing time, temperature and pressure. It’s necessary to experiment and test as needed in order to generate the desired results. Then, establish a set of standards to work by, with the full understanding that a change in the standards can lead to a change in the appearance and quality of the final product.