leVel | Diana Robinson | Digital Wallcoverings

Digital print technology has revolutionized commercial wall décor manufacturing. With its print on demand capability, digital printing allows for total customization and short run production at a fraction of the time and cost of traditional methods. However some aspects of this technology – color reproduction in particular – are often the source of confusion and misconception for prospective clients.

The following are the 5 most common areas in which a basic understanding of digital printing technology and its challenges will help properly set clients’ expectations and ultimately improve customer satisfaction.

• 1. Digital Printing Simulates Colors

  • Digital printing simulates colors using a 4 color process of Cyan, Magenta, Yellow, and Black (CMYK) inks. These inks are applied as microscopic dots of color that, when viewed with the naked eye, give the appearance of a solid color. Often the result is very close to a given target color (paint chip, carpet sample, fabric swatch, etc.) However, since this solid color is technically an optical illusion, sometimes digital printing can only provide a 'next best' alternative to the target color. And as you will see in the next few items, there are other factors that can affect the look of a digitally produced color.

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    To reproduce full-color images, typical digital printing presses use four colors of ink. The four inks are placed on the paper in layers of dots that combine to create the illusion of many more colors (the dots are printed in a pattern small enough that human beings perceive a single color). These four colors are cyan (C), magenta (M), yellow (Y), and a key, or black (K). The acronym CMYK therefore refers to the four ink colors used by the printing press. Black is referred to as the key since it is the all the other colors are registered or 'keyed' to it.

     

    In CMYK model, magenta plus yellow produces red, cyan plus yellow makes green, and magenta plus cyan generates blue. Halftoning (also called screening) allows for less than full saturation of these colors. Magenta printed with a 20% halftone, for example, produces a pink color, because the eye perceives the tiny magenta dots and the white paper between the dots as lighter and less saturated than the color of pure magenta ink. Without halftoning, the three primary process colors could be printed only as solid blocks of color, and therefore could produce only seven colors. With halftoning, a full continuous range of colors can be produced.

    The range of colors that can be simulated by this process is referred to as the color gamut. While the CMYK color gamut is quite wide, there are certain colors that cannot be achieved by it. Very saturated, bright colors are sometimes difficult to simulate. For example to make orange, magenta and yellow would be combined. In equal parts, these create a relatively bright red. If more yellow is introduced to make orange, the color tends to darken and get dull. If the amount of magenta is reduced, then the color turns out more peachy. A true, bright orange is very difficult to achieve. Likewise, very soft neutrals can be challenging. For these hues, the amount of color being applied is very minimal and the halftone percentages are very low. In this way, adding or subtracting even 1% of a color can cause dramatic and undesirable shifts.

    In short, the four color printing process is a superb technology that offers an exceptional range of color possibilities that, like any other print method, also has its limitations.

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• 2. Lighting Can Affect Your Perception of Color

  • Lighting conditions can have a significant effect on the way color is perceived — a phenomenon called metamerism. For example, any given color (real or printed) will look different when viewed under an incandescent lamp versus a fluorescent one. And colors viewed horizontally on a table can shift when placed vertically on a wall.

    

    With thousands of lighting combinations possible in the real world, it is impossible to predict or replicate the exact lighting condition of an installation during the printing process.

    'Color correct' lighting, intended to be as neutral as possible, is therefore used as an industry standard for printing. Ultimately, even with every effort to replicate a color in manufacturing, it may still vary when viewed in the installation environment.

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    Different lights have different color temperatures - the measurement of the color of light radiated by an object. Higher color temperatures (5000 degrees Kelvin or more) are cool, green-blue colors, and lower color temperatures (2700 - 3000 degrees Kelvin) are warm, yellow-red colors. For example fluorescent tubes (4000 - 6000 K) have a very cool blue cast, whereas incandescent bulbs (2700 - 3300 K) give off a warmer yellow glow. Horizontal daylight, considered to be the most neutral condition, is measured at 5000 K, which is why it is used as an industry standard for printing. As a result, the color emitted by different lights will affect the color of any object that it is illuminating.

    So a neutral beige will appear slightly more golden under an incandescent light and slightly greyer under a fluorescent light. In terms of printing, this makes color matching quite difficult. Since there is no way to exactly replicate the specific lighting conditions of an installation space, knowing what color to print in a production facility can be a bit like shooting in the dark. The use of 5000 K lights is helpful in controlling the production room conditions from one day to the next, but it still can't ensure that the colors produced will look right once installed under different lighting.

    To address this issue, whenever completely customized color is specified (any color outside of our standard chart), color grids have been introduced as a tool to help clients choose their colors. The color grid works this way: A target color is supplied by a client and a measurement is taken using the steps outlined below in 4. More About Perception. Then a grid of color swatches is created around that target, with each column and row of swatches being a step lighter or darker, warmer or cooler than the target.

    The idea is that these variances will compensate for different light conditions, such that one of them will look just right under the client's lighting. Depending on the requirements of your job, a color grid may be recommended as a tool. Please feel free to inquire about color grids though, anytime you or your client feel that they would be beneficial.

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• 3. Material Choice Can Dramatically Alter the Appearance of Color

  • Printing on different materials (substrates) can alter the appearance of color, sometimes dramatically. As inks saturate the surface of a material, they allow the color of the material to show through – think of printing inks more like stain than paint. So a color that prints as a vibrant blue on a white substrate may look greenish when printed on a substrate that has a yellow cast to it.

    

    Furthermore, even among white substrates, there is a lot of subtle variance to the pureness of the white – called white point – that can impact the look of a color.

    That said, these variations are highly predictable, and will be brought to your attention early in the specifying process. A combination of visual tools and expert guidance will help you make the right choice of substrate for your application.

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    Sometimes the effects of substrate choice on color are obvious. If you switch from a white vinyl to a tan grasscloth the color will change quite dramatically. Less obvious is the fact that even the small variances between similar substrates can affect color. The white point of substrates is a big factor. For example, assume you are looking at two Type II vinyl materials, both white, but one has a smooth finish and the other a stippled one. Both appear to be equally white, but when printed on, one yields a color that is slightly yellower than the other. Even though the naked eye doesn't perceive it, the substrate that printed more yellow has a slightly lower white point - it is inherently "yellower" by nature. This variance is normal, common, and unavoidable. And no matter what you do, that particular substrate will never yield as true a color as the other one in the example.

    Additionally, different substrates accept ink differently. Using the same example, assume now that both substrates have completely identical white points. Even still there is a possibility for color shift from one material to the next. Tiny dots of ink will lie differently on the ridges and in the valleys of the stipple finish than they will on the smooth finish. Though microscopic in nature, this difference is enough to cause a perceptible variation in the color when viewed in an application.

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• 4. Individual Perception of Color Varies from Person to Person

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    Everyone sees color differently -- a color that is a spot-on match to one person may appear to be 'off' to another. Perhaps the biggest challenge in digital printing is anticipating a client's personal sense of color.

    A device called a spectrophotometer can be used to objectively measure the difference between colors -- referred to as the Delta E difference. This device can assist in pinpointing which digitally produced color most closely resembles that of a target sample.

    However, it is ultimately up to the client to decide what 'looks right' for their application. In this way digital color 'matching' is as much an art as it is a science, and the accuracy of a color can be highly subjective. More

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    Here's how a spectrophotometer works: The target color is placed under the device's 'eye' and it's L*,a*,b* values (a device-independent method for measuring color, designed to approximate human vision) are measured. These values are applied to the specified artwork, a sample is printed and then placed under the eye for a new reading. The L*,a*,b* values of the printed sample are then compared back to those of the target color. The resulting difference is noted as a 'Delta E' value.

    The higher the Delta E value, the farther away the print is from the target. The goal is to achieve the smallest number possible, normally a Delta E difference of 3.0 or less. While this difference between a target and a printed color can be measured, the tolerance - a person's subjective assessment of a color - cannot. It is ultimately a client's tolerance for a color that determines its acceptability.

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• 5. A Little Texture Goes a Long Way

  • All printing methods have their strengths and weaknesses. In digital printing, producing large areas of solid, flat color can be challenging. Digital presses can occasionally leave banding – subtle horizontal bands that echo the left-to-right movement of the print heads across the substrate – in solid color areas.

    

    The good news is that there is a way to counteract this effect. Printing on a textured substrate like our standard recycled vinyl can obscure banding lines, and even the slight texturing of a stippled vinyl can noticeably improve the look of a print. Even so, some very subtle variation in color may still be present, and it's important to remember that this is inherent to digital printing and should not be viewed as a defect. More

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    In a digital (inkjet) press, print heads move across a substrate in a back-and-forth motion laying down tiny dots of ink as they go. On any given pass, microscopic fluctuations in the alignment of these dots can occur, resulting in the subtle appearance of subtle horizontal lines in the printed image; an effect generally referred to as banding. It is important to note that the effect described here is in fact very subtle and resembles a horizontal 'texture' effect more than harsh bands of color.

    Banding can become visible in an image that contains large areas of solid or heavily saturated colors, but is obscured by an image that has a lot of tonality, patterning, or texturing. Printing on a smooth substrate poses the greatest risk for visible banding as its’ flat, even surface exacerbates the banding effect. But as noted earlier, the uneven surface of a textured substrate (as in our standard recycled vinyl) can go a long way towards obscuring the appearance of banding, even in areas of solid color.

    That said, please note that any digitally produced wallcovering may have some inherent (and unavoidable) color inconsistency. This is normal attribute of the current technology and is not considered a printing defect.

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• In Conclusion

  Digital printing offers the best choice for custom color and design and has been a gateway to freedom of choice for the design community. As with any other print technology though, digital printing is not perfect, and cannot guarantee 100% color accuracy. This document has outlined just a few of the challenges digital printers face every day and why it is sometimes very difficult if not impossible to achieve 'perfect color matching'. The bottom line is that even the best, most expensive printers in the world must work within the constraints of the technology available to them.

  That being said, not all digital printers are the same. We pride ourselves on the fact that we not only utilize new technology and tools but that we understand the limitations and capabilities of digital printing. Because we have the support of a world-class design studio we are able to design around technological challenges to create great designs specifically tailored for your needs. Our support staff also has a deep understanding of the capabilities which allow us to create designs more efficiently, quote jobs based on real-world experience, and offer real solutions to the problems outlined above.

  Please Note: Our color tolerances meet or exceed generally accepted digital print industry standards. Our production staff makes every attempt to achieve the colors that you request as closely as possible within the current limitations of technology. We inspect all finished product under specific color-correct lighting conditions (Daylight, 5000 degrees Kelvin, D50 bulbs).

  For an accurate sample of your final production color, scale, layout, and substrate you must order a strike-off.

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