The Digital Illustration Edge

When it comes to creating illustrated imagery, one type of element that is important in every illustration, and is often taken for granted is an edge. In the non-digital illustration world edges are created by the physical use of an art material, but in the digital world, edges must be created in a virtual way to simulate a non-digital visual appearance. Image software programs like Adobe Photoshop provide both automated and user defined ways to manipulate an edge. So, as is the case with every aspect of a digital image, the illustrator has the ability to influence the look of edges in their work. It’s helpful to know how digital edges are rendered and displayed.

Anti-Aliasing

A good explanation of anti-aliasing begins with a good description of display aliasing. Basically, aliasing is a jagged or stair-step appearance that is caused by a lack of resolution either by restrictions in a hardware device, such as a display, or file size limitations in a raster-based document. Anti-aliasing is the technique software designers have adapted to reduce or eliminate jagged edges by fooling the eye of the viewer. This is done by creating a diminishing series of shading steps between the edges of adjacent colors. See Below. Anti-aliasing is also referred to as “smoothing”.

Closeup of aliased stair step in red, anti-aliased smoothing in blue.

Aliased mountain rendering. © 2012 Don Arday.

Anti-aliased mountain rendering. © 2012 Don Arday.

Closeup of the anti-aliased edge of a rose petal.

Interpolation

Anti-aliasing occurs through the interpolation of picture elements, “pixels”. Think of interpolation as swapping and sharing. To improve the digital visual appearance of an image on our monitor the technique of interpolation is used. Let’s refer to the data in an image as a sample. To make the image display better, the computer converts the image to a higher sample by using filtering techniques like anti-aliasing. It may be no coincidence that the word interpolation bears a resemblance to interpretation, because that is sort of what occurs within anti-aliasing. The software in the case of a document, or the computer video card in the case of the display, interprets the color relationships when attempting to create a smooth transition between one color and another to render edge pixels. This generally occurs automatically, but illustrators can use manual methods to control the appearance of edges within their illustrations.

Dithering

Dithering is often confused with anti-aliasing, but it is actually something quite different. Dithering most often occurs in color image situations where colors in an image are out of the range of the colors available in an image display or output device. When this occurs the software program creates the unavailable color by mixing other colors that are available. For example, dithering can occurs when a particular web browser does not support a specified color. The browser will then attempt to mix the requested color by “dithering” pixels by using a combination of other colors it can produce.  Although usually invisible to the naked eye, dithering is done in the same manner as “noise” is, (see below) and like noise, it can appear slightly grainy in the extreme.

Some Manual Techniques

Feathering

Feathering is the softening of edges of adjacent shapes and colors within an image beyond the standard level of interpolation. Adobe Photoshop gives you the option to feathering selection edges in an image. A feathered edge results in increased edge blurring and a lowering of edge contrast between colors. With feathering, the artist has the ability to control the number of pixels to be included in a feathered edge. The result of feathering is similar to that of Gaussian blur. (See below.)

Gaussian Blur

Using Gaussian blur, or any of the other blur options in raster programs, means to force adjacent colors to drift into one and other creating a smoother edge transition. Colors in a Gaussian blur drift in a randomly distributed, non-linear manner. A motion blur option of the Gaussian blur limits the random color distribution to a particular direction. Blur can be used to redefine edges, and it can also be used to control the amount of focus in an image.

Gaussian blur applied to complimentary colors.

Gaussian blur closeup.

Noise

Although a controllable option in Photoshop, and a very useful one, noise, and specifically random pixel noise is not necessarily thought of a s a good thing. Pixel noise is an unnatural, or unwanted, variation of value or color information in an image. Noise has a tendency to degrade sharp edges within an image by producing a scattered effect of random colored pixels. So a yellow flower against a blue sky may end up with blue pixels mixed among the yellow ones. And the flower and the blue sky might both have red pixels scattered in as well. See below. Photographers generally find noise to be very disturbing, however for the illustrator it may help to produce a desired, even naturalistic color effect. Noise is best applied as a final stage before publishing an illustration. And once saved an illustration that has had noise added is permanently altered, so it is always best to save your illustration prior to using noise, then save the noise applied version as a separate file.

Noise applied. Note the addition of other color pixels to the original pair
of complimentary colors.

Noise closeup.

Sharpening

The three techniques discussed above can produce a smoothing appearance to an edge, but they also degrade its sharpness. Using a sharpening filter or “Unsharp Mask” in Photoshop can give the appearance of actually sharpening edges. Sharpen filters identify where dark and light edges meet in an image, and add contrast to those edges. The filter does this by creating an even darker line along the edge of a dark shape, and also a lighter line on the edge of an adjacent light shape. Unsharp Mask tends to move edges away from an anti-aliased appearance, and taken to far, sharpening can produce a very unnatural looking halo around shapes. See below. Sharpening like noise is best applied as a final stage before publishing an illustration.

Edge sharpening applied. Note the increased contrast at the edges of
the two colors.

Edge sharpening closeup.

There are also some techniques in Photoshop for working with edges that rely on methods of selection like “Refine Edge” and “Fringe”, but the result of any of those actions uses the above basic methods of rendering.

By understanding how digital image edges are rendered and by using these manual options for refining them, you will have greater control over the appearance of your illustration either in print or on the monitor.

Archival Digital Art

“I’m a digital artist. All the images I have made in recent years are ‘virtual’".

I remember when photographic film manufacturers used the word “archival” when describing color film and prints. In the 1980’s and early 1990’s, after a quarter of a century the images many of us documented our lives with began fading beyond recognition. And the highly prized photographic work of renowned artists and photographers was in danger of becoming worthless. About the time color chemically produced prints began to show signs of degradation, digital printing devices began to hit the market. Although originally developed as proof printing devises for the printing industry, inkjet color laserwriters, and dye sublimation printers showed promise to be the saviors of artistic and photographic image printing. In the early 1990’s, with little concern about the composition of inks and the rag content of paper used by the printer manufacturers, digital printers could only hope for the same shelf life as the emulsion sensitized color prints that preceded them.

Digital Data Lifespan

It is highly advisable to store important images and digital information using multiple sources and to periodically transfer the data from old archive storage to new storage. Top manufacturers like Mitsui, Verbatim, Maxell, Memorex and TDK claim that premium compact discs, with protective coating and special dyes, will last from 50 to 200 years for CD-R’s and somewhat less for CD-RW’s, although I’ve had disks become unreadable after about ten years. Third generation flash memory is estimated to have a lifespan rating that is based on the number of erase/write cycles instead of a time span. The maximum number is approximately from 10,000 for multi-level cell (MLC) memory to 300,000 writes for single level cell (SLC) memory. The type used on the MacBook Air and the iPad is MLC. Magnetic platter hard drives, the drives in most computers, are estimated to last from 3 to 7 years, however treated well many drives that last longer than that. I recently booted up a hard drive that I mothballed in 1995.

It is also highly advisable to periodically open up older files in new updated versions of software and resave them. Regarding that data on that drive from 1995, I copied it and transferred it to my new Mac, which runs current versions of Adobe and Microsoft software. I found there were files that were simply too old to be recognized by current software. Know that the concept of universal upward compatibility was not always around, nor will it necessarily be around in the future.

“Never trust the technology. Always be prepared for the unexpected.”

Digital Prints

There are two factors that determine whether digital prints are archival, the paper and the ink. Through testing projections, manufacturers try to predict the future permanence of their products. As digital image makers we rely on these products and those predictions.

For several years I have used an Epson Stylus Photo R1900 printer, which uses Epson UltraChrome Hi-Gloss pigmented ink with clear “gloss-optimizer”. It’s a 7 color pigmented inkjet system. I print on Epson Watercolor Paper Radiant White Matte coated fine art paper, as well as a number of different kinds of fine art 100% cotton rag papers. Wilhelm Imaging Research, Inc. rates the above combination with the Epson paper to have an archival longevity of 200 to 300 years.  Resource: http://www.wilhelm-research.com/epson/R1900.html

“A digital print gives digital work a physical legacy and form of permanence”.

The Paper

100% rag cotton fiber rag quality paper is estimated to remain stable for between 250 to 300 years. Seizing on an opportunity, paper manufacturers with hundreds of years of experience in making archival papers for the fine arts, decided to renovate their tried and true paper formulas for digital printing. Canson, who makes a variety of digital papers including BFK Rives and Arches, was founded in 1557. Both of those 100% rag papers are available for digital printing. Since 1584, Hahnemühle has been making superbly crafted, unique, beautiful papers. Their papers are available for digital output. Crane & Company, which began in the mid 18th century, the same company that supplies the paper used for US currency, makes the Museo line of papers for digital printing. These papers are acid free with 100% rag content. So some of the finest papers for digital printing are available for our use.

The Inks

Ink color changes over time. The change can appear as a lightened washed out look or a flattening of brightness and contrast. Early producers of inkjet prints were astounded to discover that their prints faded within months. The environmental factors contributing to fading are light, temperature, humidity, etc. Museums and galleries place tremendous importance on carefully controlling light levels and humidity. With a digital print, the ink itself, the type of color dyes or pigments used, can also contribute to a lack of color stability.

Dyes

Printing inks now come in two main forms, as dyes or as pigments. Just a few years ago, all inks for inkjet printers were dye based. Dyes make very rich colored prints but are susceptible to fading. Ink manufacturers have also developed archival dye-based inks that are now available. Archival dye inks are less expensive than pigment inks. Some are very hardwearing and appropriate for the needs of most consumers. If well taken care of, prints may last for several generations.

Pigments

Over the past few years, ink manufacturers have made significant advances in combating fading by introducing pigment-based inks. Pigments are much more resistant to fading than dyes. Pigment is permanently colorfast, stable, and enduring, making it the superior choice for archival material. Archival pigment-based inks are more costly than dye-based inks. Governments print important documents with pigment-based inks to preserve them for the future.

In Conclusion

The future may hold changes such as the addition of new file formatting options and the elimination of old ones. SCSI and PS2 cables have become history. Will USB, Firewire and other computer connectors also become obsolete? Because of this, it is important to establish a system for archiving and preserving your digital work, and to consider transitioning through changes in hardware equipment along with advances in software technology.