Every once in a while an experience touches our hearts and minds. Something that makes us glad to be alive. Something that makes us treasure our senses; our ability to touch, smell, taste, hear and see. These senses enhance our awareness of who we are and allow us to fully experience all that this wonderful world has to offer.
All across the world, in different industries and environments, there is rarely just one message that speaks to everyone. Rarely one work of art or piece of literature that appeals to all. But, occasionally there are events that surpass the natural division and bring people together. A common experience that everyone can connect with in their own way.
In the competitive world of marketing it is often difficult to appeal to a broad market and especially challenging to connect with them in a memorable way. The media noise and bright abundance of competition can distract your audience and cause them to loose focus. There is one form of media, however, that is simple and truly appeals to the senses – print.
A unique experience. Something to hold, to feel, to read and reflect upon. Imagine a media that has changed the world, which has been a part of human communication for thousands of years. A media that is real, bold, and inspiring, maybe even transcendent.
It’s not just the feel of the paper. It’s not just the words or the graphics or quality of printing. It is everything together…the experience.
It’s alive! At least it was. Love it or hate it, paper has a place in our world. And, not just as paper bags and note pads. Paper is abundant in packaging, building materials, marketing materials, and of common disposables like paper towels and toilet paper. It is everywhere. Though paper often gets a bad wrap, the case for using paper may not be as thin as you think.
It’s no secret that the main ingredient in paper is trees. Don’t get me wrong; I am a tree lover myself. We all should be, after all, forests are necessary for human survival. By absorbing large amounts of carbon dioxide and providing oxygen in return, forests around the world provide a large percentage of the air we breathe. But, considering the alternatives of competing plastic products there are some compelling arguments for using paper. Consider a simple grocery bag. It may take 10-20 years to grow a tree for a paper bag. It can take millions of years to create the crude oil for a plastic bag. The plastic bag also takes hundreds or thousands of years to biodegrade whereas the paper bag will be back into the earth in less than a week. Trees are a renewable resource. Growing and processing trees is sustainable when managed responsibly. When oil is gone, it’s gone. And, it is estimated there is only about 100 years worth of oil left on earth. There is no solution that is totally friendly for the environment though. All mass-produced products use energy in some form or another. All have some amount of waste or environmental impact associated with them.
In regards to shopping bags, packaging, or household items, there are other alternatives besides paper or plastic. The “right” choice of material in these categories can be debated and discussed in depth. However, for purposes of this article, I am going to focus on paper for marketing materials; particularly, high quality sheets of paper that are used by print providers in the production of brochures, direct mail, and other marketing collateral.
Through organizations like Rainforest Alliance and Forest Stewardship Council (FSC), forests all over the world are being managed in a way that not only maintain the health of a forest, but can also increase its size. Through sustainable forestry practices and the development of plantations, forest cover in the U.S. has increased by almost 30 million acres over the last 15 years. In contrast, forest cover in South America has decreased about 150 million acres in that same time period. Although the ability of the FSC and other organizations to prevent deforestation in developing countries has increased greatly over the years, their control is still limited and presented with major challenges due to socioeconomic and cultural factors. For this reason, when choosing a print provider, it is important that you know where they are sourcing their paper. Some print providers use cheap imported sheets from China and developing countries that are less controlled when it comes to the harvesting of trees.
The production of paper is a fascinating and surprisingly efficient process. Trees are harvested, debarked, and converted into small chips at a pulp mill. The bark is used as fuel to help power the mill. The wood chips are mixed with a natural acid and heated in a giant pressure-cooker called a digester. This cooking process separates the lignin from the plant fiber. Lignin is the liquid that binds the plant fibers together. The lignin byproduct, called black liquor, is also used as fuel to help power the mill. The plant fiber pulp is cleaned further to remove all remaining lignin, leaving the pulp bright white. The pulp is then dried, baled and sent to the paper mill to be used as the main structure for paper.
At the paper mill the pulp is mixed with water and formed into a paper web through a series of large cylinders. This process begins with the liquid pulp being dispersed between two large cylinders that compress the pulp and rapidly remove water to form the initial paper web. The paper web then continues through a series of metal cylinders and felt surfaces to further compress and dry the paper web until it is self-supporting. The paper web is then finished by applying a coating to create a gloss or matte surface (referred to as coated), or left raw (referred to as uncoated). The uncoated paper can also be compressed further to smooth it or create texture.
When choosing a paper for your print project, there are four general factors to consider: type, weight, finish and color.
Paper type: Paper is categorized in two general types: coated and uncoated. Coated stocks have a coating that provides a smooth surface and reduces how much the ink soaks into the paper; this yields brighter colors and sharper images. Common coated stocks include gloss, silk, satin, dull and matte. Satin, dull and matte stocks are often very similar, and sometimes indistinguishable, between different paper manufacturers. Uncoated stocks are just that; they do not have a coating. This allows ink to completely soak into the paper and yields softer color and images. Uncoated stock is good for reading because it has no glare. It is also best for writing and is used for letterhead and other stationery items. Uncoated stock should not be confused with matte paper, which is a coated stock.
Paper weight: Typically used to reference the thickness, paper weight is often measured by pound within categories of text and cover. Common weights from lightest to heaviest are 60lb. text, 80lb. text, 100lb. text, 80lb. cover, and 100lb. cover.
Paper finish: The paper finish involves surface treatments that create or reduce texture. Finish is mostly a factor when referencing an uncoated stock. Common finishes include smooth, super smooth, vellum, felt, linen, columns and canvas.
Paper color: The most available color is white, as one would guess. Though, just as in paint, there can be several shades of “white.” Most coated stocks only come in a single shade of white within a paper line. Uncoated stocks, however, are available in several shades of white as well as a variety of colors such as natural, crème, pastels and vibrant colors from black to florescent orange. There are also specialty papers such as metallic and pearlescent sheets that come in a variety of colors and can add a level of sophistication.1
1philprint.com/resources/FAQ
The journey of paper from the forest to your mailbox is a complex one, and one that is often misunderstood. Paper has many uses within our consumable and marketing environments. If you are looking for the right paper for your printed collateral, marketing brochures, booklets, or direct mail, ask your print provider for recommendations. Printers and paper houses can provide swatch books from different mills so you can make the best choice for your print project.
You can get from point A to point B in many different ways. You could walk, run or drive a car. You could ride a bike, take a train or fly in a plane. There is usually more than one way to do anything. This is just as true for printing as it is for traveling.
Though there may be many methods to achieve the same result, there are usually reasons for choosing one method over the other. When traveling, for instance, you wouldn’t typically walk from Chicago to Los Angeles, and it would be just as illogical to take a plane across town. There is similar reasoning when it comes to deciding which method of printing is best suited for each project.
When Johannes Gutenberg invented the moveable type printing press in the early 15th century he likely had no idea how it would change the world. His combination of adjustable letter molds, moveable type, ink, and a wooden corkscrew press comprised a device that allowed the mass production of written communications. The distribution of printed texts of religion, education and politics created a revolution like few other inventions ever have. As literacy boomed, printing allowed ideas to be spread throughout society at a rapid pace. Gutenberg’s most famous printed work was his 42-line Bible of which dozens of copies still exist today.
There may indeed be 1001 ways to print if one were to really explore the possibilities. If we define print as mechanically transferring pigment from one substrate to another, there is a huge number of variations one could consider a printing process – from squeezing sheets of vellum under a wooden press to printing tens of thousands of sheets per hour on a web press. There are certainly more ways to print than anyone would care to know, so I won’t attempt to go through them all. Here a few of the most common methods of printing, types of printers, and their intended uses.
Letterpress Printing A letterpress is a direct relief printing process and is what the early presses of the Renaissance period were. A letterpress involves individual blocks of wood or metal with a raised character on one end. These blocks are put into a frame, arranged to form the desired message or design, and ink is applied to the raised surface. The inked letters are then directly pressed onto a paper sheet or roll. Few letterpresses are still in operation today, though there are a few novelty shops that still use them to create authentic or artistic printed works.
Digital Printing Digital printing refers to any printing process where the image on the substrate is directly produced through a digital signal. Digital printing is best suited for relatively small runs and variable imaging. Digital printing devices generally use either inkjet printing technology or laser printing technology. Most home desktop printers fall into one of these two categories.
Inkjet Printing Inkjet printing is a form of digital printing that uses a print head mechanism that sprays very regulated droplets of ink directly onto a substrate. Inkjet printers usually produce full-color images. Inkjet printers are best suited for single or small print runs and variable imaging. Inkjet printing is utilized in the commercial printing industry for proofing due to its large color gamut and consistent reproduction capabilities. It is also used in wide format applications to produce large prints like billboards and full-color banners. Inkjet printers intended for high-quality imaging and proofing can print substrate sizes from 8.5 inches to 4 feet wide and use up to 11 different colors for process printing. Some grand format inkjet printers can be as large as 16 feet wide!
Laser Printing Laser printing is a form of digital printing that uses a laser-powered imaging system to transfer an image of toner to a metal drum. The toner is then transferred from the drum to a transfer belt, which transfers it to the paper. The toner on the paper is then heated by a high-temperature roller, which fuses the toner image, instantly curing it. Laser printers are best suited for small to medium print runs and variable printing. Most commercial digital presses utilize laser-printing technology and are used for products such as brochures, postcards and personalized printing.
Impact Dot Matrix Printing The first desktop computer setups often included a dot matrix printer. You may remember that unforgettable zapping sound and the fun of creating long happy birthday banners. Impact dot matrix printers involve a computer-controlled print head that strikes the paper through an ink-covered ribbon and creates letters or patterns with a matrix of dots. Impact dot matrix technology is still used today in such devices like receipt printers.
Thermal Printing Thermal printing is similar to laser printing but uses a coated film that is drawn between a fusing head and the substrate. When the fusing head selectively heats the film the coating is fused to the substrate. Thermal printers are typically small and used primarily for label and/or vinyl printing.
Dye-sublimation Printing Dye-sublimation is a process used to print on polyester and polyester resin-coated products such as fabric or tiles. Dye-sub inks are used to first print an image on a special transfer paper and then, through heat and pressure, the image is transferred to the substrate. Sublimation refers to the process of the solid toner transforming directly into a gas, bypassing a liquid state, and penetrating the polyester fibers.
Screen Printing Screen printing is a direct to substrate process that involves a fine mesh screen that ink is pressed through onto the substrate. Certain areas of the screen are blocked out to prevent ink from passing through creating the desired design. Screen printing is often used in textile printing (t-shirts, fabric, etc.) and for larger print runs of small signs.
Offset lithography (referred to as offset or litho for short) is a rotary offset printing process that involves an imaged metal plate that transfers an inked image to a rubber blanket, which then transfers the image to the substrate. Lithography works on the basic principle that oil and water do not mix. The image plate has a thermal or light-sensitive coating that is exposed through a laser process in a CtP (computer-to-plate) device to create the image. The plate retains ink where it has been imaged and water repels ink where the plate has not been imaged. Offset refers to the fact that the image plate does not make direct contact with the substrate. Lithography setup cost is less than that of flexography or gravure and is best suited for efficient high-quality printing of medium to long production runs. Most high-volume commercial presses use offset lithography.
Flexography Flexography (referred to as flexo for short) is a rotary relief printing process that involves a flexible image plate that applies ink directly to the substrate. The basic principle is very similar to letterpress printing. The relief aspect of the image plate allows for printing on a variety of surfaces such as cardboard and other similar uneven substrates. Flexographic setup costs are relatively high and it is best suited for long production runs or products requiring relief printing. Unlike lithography, which uses oil-based inks, flexography (and rotogravure) can utilize water-based inks, which allows for printing on a wider array of substrates.
Rotogravure Printing Rotogravure (referred to as gravure for short) is a rotary direct printing process that involves an etched metal plate containing cells that hold the ink to be transferred directly to the substrate. The depth of the cells determines the amount of ink carried, creating more or less ink density. Unlike flexography or offset lithography, the gravure plate is in direct contact with the ink fountain. Most gravure presses print on rolls of paper known as webs. Rotogravure setup cost is very high but the etched metal plates last for a long time without deterioration which makes gravure printing best suited for very long production runs with undiminishing quality.
UV Printing UV printing involves using inks containing photoinitiators (light-sensitive molecules) that cause the ink to cure when exposed to ultra-violet light. Ink can be applied to a substrate and then cured instantly (changing from a liquid to a solid) with UV light so there is no absorption, dry time or issues during finishing processes. There are several print methods that utilize UV technology. UV screen printing is often used in commercial printing to apply gloss coatings or specialty effects. Flatbed inkjet printers, which can print directly to rigid substrates, utilize UV technology. UV light is also used to cure inks in various high-speed printing processes such as lithography and flexography. UV printing has become more and more popular in commercial printing due to its production efficiency benefits. UV inks are also 100% solvent-free so there is no emission of VOCs (volatile organic compounds) or hazardous air pollutants.
Sheetfed Presses A sheetfed press refers to any press where a pre-cut sheet is fed through the press. The sheet can be paper, plastic, cardboard, or other material. Though sheetfed typically refers to offset lithography, it can also include flexography or rotogravure printing processes. Sheetfed presses run at speeds as high as 18,000 sheets per hour and are best suited for medium to large print runs. They are often used to produce high volumes of postcards, packaging materials and brochures.
Web Presses Unlike a sheetfed press, a web press uses continuous rolls of paper instead of individual sheets. The large machines seen in movies running newspapers and taking up an entire room are web presses. Finishing processes such as cutting, collating and folding are often done inline. Web presses can utilize lithography, flexography or rotogravure methods to transfer ink. Web presses run at speeds of thousands of feet per minute and are best suited for very large print runs. They are often used to produce high volumes of newspapers, magazines and catalogs.
There are several variations of the processes and printers listed above, but hopefully this gives a little insight into the basic methods that can be used to produce a printed image. More information on the printing process and other related aspects can be found at philprint.com/resources/faq.
As the old saying goes, there is more than one way to screen a cat…the image of a cat that is–a little printing humor there. All lame puns and disturbing metaphors aside, I am referring to the different types of screening in lithographic printing. Within any manufacturing process there can often be multiple production method options with pros and cons in each. In addition to a general explanation of the process, I will discuss the benefits and challenges of two of the standard screening methods used in offset lithographic printing.
What is a screen?
In printing, a screen can refer to a tint of a single color and/or a resolution of sorts. A lighter tint of black would produce gray, and how smooth that gray is could be considered the resolution, or line screen (lines per inch)–which I’ll discuss later. The type of screening refers to the tint, particularly, how the tint is produced. Imagine a screen door material that has holes in it to allow air to pass through. Now imagine putting that material on top of a piece of paper and pressing ink through the screen. The size of the holes and the number of holes would determine how much ink gets to the paper. Less holes or smaller holes would allow less ink, yielding a lighter tint, whereas more holes or larger holes would allow more ink, yielding a darker tint. This is basically how screen-printing works. Screen-printing involves using an emulsion process to block out areas of a fine mesh to control the ink applied to a substrate. The ink is applied directly through the mesh to the substrate. Each color has its own screen and is applied one at a time. It is primarily used for simplistic designs in textile printing and high-volume signage.
The process in lithographic printing is similar, except the “screen” that determines the tint is imaged onto a metal plate which transfers the ink to a rubber blanket which then transfers it to paper. This process is also called offset printing. Most printers use CMYK process to produce full-color images. With CMYK process all colors are reproduced through the combination of four base colors–cyan, magenta, yellow, and black. Each of these colors is printed in various tints and combinations to produce all the colors we see in images and graphics. How the tint is produced for each color is referred to as the screening method.
Screen types
There are two types of screening methods used in lithographic printing. The first, and most common, is amplitude-modulated screening (AM screening). This method uses a fixed dot pattern. As the tint gets darker the size of each dot is increased, as the tint gets lighter the size of each dot is decreased, but the number of dots in a given area stays the same.
AM screening is commonly used among printers due to its controllable nature. Most printing plates and blankets available on the market today can easily support a standard AM screen and there is less sensitivity in how well the ink is carried and transferred to the paper. Although, the quality and balance of consumables and proper calibration will always greatly affect the level of quality and consistency that can be achieved.
Because AM screening uses a fixed dot pattern, each of the four CMYK process colors must be at different angles so that the dots do not line up on top of each other. The four colors are typically at (Y) 0˚, (C) 15˚, (K) 45˚, and (M) 75˚. However, this combination of the same pattern at different angles creates a rosette pattern and is one of the well-known drawbacks of AM screening (figure 5). If you look at any full-color printed piece with a magnifying glass or loop you will likely be able to see this pattern of interlocking circles.
The second type is frequency-modulated screening (FM screening). FM screening is also referred to as stochastic screening. This method uses a very small fixed dot size. As the tint gets darker the number of dots is increased, as the tint gets lighter the number of dots is decreased, but the size of the dots stays the same.
FM screening has many advantages when reproducing fine images. Because FM screening utilizes a small random dot pattern, the level of detail and smoothness that can be achieved is far greater than with AM screening. FM screening does particularly well in reproducing high-resolution images of fabric, leather, skin tones or any image where there are very fine details in the textures. Another drawback with AM screening is the potential to produce a moiré effect. Though, a moiré is most often seen when reproducing a scan of a printed piece resulting in a multiplication of the rosette pattern, it can also occur when reproducing an image with a fine geometric pattern like fabric. This is because the rosette pattern of the screen can interact with the pattern of the fabric. This is not an issue with FM screening because there is no consistent pattern to the dots. FM screening also tends to use less ink because there is more dot gain (as there are generally more dots) – meaning less ink is required to produce the same visual tint.
Line Screen
AM screening also involves a line screen. A line screen is the number of halftones per inch, expressed as lines per inch (LPI). This determines how fine the dot pattern is, or how close together the dots are. The closer together the dots are the higher the resolution that can be achieved. However, with higher resolution and finer dots come more challenges in maintaining a consistent result or a smooth image. Most sheetfed lithographic printers will run a 133 to 175 line screen. This is high enough to produce a very smooth image and still be somewhat forgiving. There is also a type of screening that utilizes both methods called hybrid screening. Hybrid screening is primarily AM screening, but at tint values below 5% and above 95% it uses FM screening. This allows for smoother transitions and imaging in highlights and shadows.
FM screening does not use a line screen because the size of the dot is fixed and the pattern is considered random. The equivalent aspect for FM screening would be the size of the dot, which is measured in microns. Most printers running stochastic will use a 20 to 30 micron dot size. Not all printing plates can handle maintaining a clean dot that size. Even if the platesetter (CtP) can image the dot, the plate surface must be able to maintain the dot during printing. If the dot erodes during printing the image will start to disappear or become lighter. This erosion of the plate image is called blinding. The fountain solution, which is the water/chemical solution that keeps the plate clean where there should not be ink (the water versus oil principle), can also play a part in whether blinding occurs.
You may be wondering why, if FM screening looks so much better and uses less ink, more printers don’t use it. In addition to some of the potential challenges mentioned above, there is usually an additional license purchase and it does take a lot of effort in creating and maintaining proper calibration as well as discovering the right balance of consumables to yield a consistently good result. However, with diligent color management, equipment maintenance, and the right consumables, stochastic screening can be a huge benefit to the printer and produce a much higher quality product for the client.
Phillips utilizes both hybrid and stochastic screening methods and is G7 color-space certified in both. If you would like to see examples of printed pieces using these different methods or have any questions, feel free to contact us or call us at 888-ask-phil.
One of the biggest challenges with producing any custom product is setting the customer’s expectation before production begins. This is true in many industries and it is no less of a challenge in printing. The reason for this is that the equipment that produces a single printed proof typically uses a different printing method and material than the press that will produce the piece in high volumes.
A contract proofer typically uses an inkjet printing method whereas high-volume commercial presses use lithographic (offset) or flexographic printing methods. There are also toner-based digital printers that can be used for both proofing and production. Inkjet printers spray ink onto specialized stocks compatible with inkjet technology. Lithographic and flexographic presses use a series of rollers to transfer ink to paper. Inkjet proofers typically use 6 to 11 colors to produce full-color images. A lithographic press usually uses only 4 colors–cyan, magenta, yellow, and black–to produce full-color images. These different methods of production naturally result in differences in color, finish, and capability. The type of paper also plays a roll in the color that will be produced. A gloss sheet will have vibrant, high-contrasting color, and an uncoated sheet will have lighter, more muted colors. The challenge is both targeting each piece of equipment to a given standard (or to each other) and hitting that target with consistency.
We accomplish this by first fine-tuning the prepress and press operations including PDF workflow, CtP calibration, plate linearization, ink consistency, press consumables, press mechanics, and press operation consistency. If the process and elements involved in producing color is constantly changing then it does no good to hit a given target when the starting point could be different from day today. Much like leveling a house on an unstable foundation. Once this process is stable with an established baseline we use a combination of dot gain curves and ICC profiles to adjust the color. Color charts with thousands of patches are scanned and analyzed to create ICC profiles. This process usually takes several rounds to get the printed result off press to a G7 colorspace standard. A similar process is then applied to the proofer and digital presses. There are two ways to go at matching the proofer to the press. One could use the output of the press as the target for the proofer. This would tend to be more accurate within a company for a given press but could result in the proofer having a higher Delta E than it could achieve for the standard target. It would also isolate that company’s color to its press as opposed to meeting a global standard. Another way is to use the same G7 standard as the target for the proofer. As long as the press is able to achieve a low Delta E for the same target then this would allow the press and proofer to rely on each other as a common reference with the proofer having the lowest Delta E possible for the standard target. There are different standards for coated and uncoated papers and coincidentally separate processes to achieve and/or simulate the color standard on each.
There are different proofing stocks for inkjet printers for simulating coated versus uncoated products. Coated stocks will have a glossy surface and uncoated (typically called matte for inkjet media) will have a rougher non-glossy surface. One element that limits an ICC’s ability to simulate color between the proof and press is the base white point of the proofing stock. This is measured in whiteness, which is a paper’s ability to reflect all colors equally under D65 lighting conditions, and brightness, which is the amount of blue light the stock reflects. Brightness is also affected by the amount of optical brightening additives in the paper, which can make the paper appear bluer. It is important that the white point of the proofing stock be as close as possible to the white point of the offset stock. This establishes a comparable base between the two media and allows the proofer to more closely simulate the full-color gamut of the press.
Phillips Printing uses an 11-color inkjet proofer to produce contract proofs that very closely simulate the color we can achieve with our offset presses on both coated and uncoated stocks. Our offset press, proofer, and digital presses all meet Idealliance colorspace standards. Setting our clients expectations at the proofing stage has proven to be a valuable asset by greatly limiting any surprises with the finished product. It also allows us to fine tune graphics with accuracy to make sure our clients get what they want. To learn more about proof-to-print and G7 grayscale/colorspace certifications visit idealliance.com or contact us.
As the old saying goes, there is more than one way to screen a cat…the image of a cat that is–a little printing humor there. All lame puns and disturbing metaphors aside, I am referring to the different types of screening in lithographic printing. Within any manufacturing process there can often be multiple production method options with pros and cons in each. In addition to a general explanation of the process, I will discuss the benefits and challenges of two of the standard screening methods used in offset lithographic printing.
What is a screen?
In printing, a screen can refer to a tint of a single color and/or a resolution of sorts. A lighter tint of black would produce gray, and how smooth that gray is could be considered the resolution, or line screen (lines per inch)–which I’ll discuss later. The type of screening refers to the tint, particularly, how the tint is produced. Imagine a screen door material that has holes in it to allow air to pass through. Now imagine putting that material on top of a piece of paper and pressing ink through the screen. The size of the holes and the number of holes would determine how much ink gets to the paper. Less holes or smaller holes would allow less ink, yielding a lighter tint, whereas more holes or larger holes would allow more ink, yielding a darker tint. This is basically how screen-printing works. Screen-printing involves using an emulsion process to block out areas of a fine mesh to control the ink applied to a substrate. The ink is applied directly through the mesh to the substrate. Each color has its own screen and is applied one at a time. It is primarily used for simplistic designs in textile printing and high-volume signage.
The process in lithographic printing is similar, except the “screen” that determines the tint is imaged onto a metal plate which transfers the ink to a rubber blanket which then transfers it to paper. This process is also called offset printing. Most printers use CMYK process to produce full-color images. With CMYK process all colors are reproduced through the combination of four base colors–cyan, magenta, yellow, and black. Each of these colors is printed in various tints and combinations to produce all the colors we see in images and graphics. How the tint is produced for each color is referred to as the screening method.
Screen types
There are two types of screening methods used in lithographic printing. The first, and most common, is amplitude-modulated screening (AM screening). This method uses a fixed dot pattern. As the tint gets darker the size of each dot is increased, as the tint gets lighter the size of each dot is decreased, but the number of dots in a given area stays the same.
AM screening is commonly used among printers due to its controllable nature. Most printing plates and blankets available on the market today can easily support a standard AM screen and there is less sensitivity in how well the ink is carried and transferred to the paper. Although, the quality and balance of consumables and proper calibration will always greatly affect the level of quality and consistency that can be achieved.
Because AM screening uses a fixed dot pattern, each of the four CMYK process colors must be at different angles so that the dots do not line up on top of each other. The four colors are typically at (Y) 0˚, (C) 15˚, (K) 45˚, and (M) 75˚. However, this combination of the same pattern at different angles creates a rosette pattern and is one of the well-known drawbacks of AM screening (figure 5). If you look at any full-color printed piece with a magnifying glass or loop you will likely be able to see this pattern of interlocking circles.
The second type is frequency-modulated screening (FM screening). FM screening is also referred to as stochastic screening. This method uses a very small fixed dot size. As the tint gets darker the number of dots is increased, as the tint gets lighter the number of dots is decreased, but the size of the dots stays the same.
FM screening has many advantages when reproducing fine images. Because FM screening utilizes a small random dot pattern, the level of detail and smoothness that can be achieved is far greater than with AM screening. FM screening does particularly well in reproducing high-resolution images of fabric, leather, skin tones or any image where there are very fine details in the textures. Another drawback with AM screening is the potential to produce a moiré effect. Though, a moiré is most often seen when reproducing a scan of a printed piece resulting in a multiplication of the rosette pattern, it can also occur when reproducing an image with a fine geometric pattern like fabric. This is because the rosette pattern of the screen can interact with the pattern of the fabric. This is not an issue with FM screening because there is no consistent pattern to the dots. FM screening also tends to use less ink because there is more dot gain (as there are generally more dots) – meaning less ink is required to produce the same visual tint.
Line Screen
AM screening also involves a line screen. A line screen is the number of halftones per inch, expressed as lines per inch (LPI). This determines how fine the dot pattern is, or how close together the dots are. The closer together the dots are the higher the resolution that can be achieved. However, with higher resolution and finer dots come more challenges in maintaining a consistent result or a smooth image. Most sheetfed lithographic printers will run a 133 to 175 line screen. This is high enough to produce a very smooth image and still be somewhat forgiving. There is also a type of screening that utilizes both methods called hybrid screening. Hybrid screening is primarily AM screening, but at tint values below 5% and above 95% it uses FM screening. This allows for smoother transitions and imaging in highlights and shadows.
FM screening does not use a line screen because the size of the dot is fixed and the pattern is considered random. The equivalent aspect for FM screening would be the size of the dot, which is measured in microns. Most printers running stochastic will use a 20 to 30 micron dot size. Not all printing plates can handle maintaining a clean dot that size. Even if the platesetter (CtP) can image the dot, the plate surface must be able to maintain the dot during printing. If the dot erodes during printing the image will start to disappear or become lighter. This erosion of the plate image is called blinding. The fountain solution, which is the water/chemical solution that keeps the plate clean where there should not be ink (the water versus oil principle), can also play a part in whether blinding occurs.
You may be wondering why, if FM screening looks so much better and uses less ink, more printers don’t use it. In addition to some of the potential challenges mentioned above, there is usually an additional license purchase and it does take a lot of effort in creating and maintaining proper calibration as well as discovering the right balance of consumables to yield a consistently good result. However, with diligent color management, equipment maintenance, and the right consumables, stochastic screening can be a huge benefit to the printer and produce a much higher quality product for the client.
Phillips utilizes both hybrid and stochastic screening methods and is G7 color-space certified in both. If you would like to see examples of printed pieces using these different methods or have any questions, feel free to contact us or call us at 888-ask-phil.
One of the biggest challenges with producing any custom product is setting the customer’s expectation before production begins. This is true in many industries and it is no less of a challenge in printing. The reason for this is that the equipment that produces a single printed proof typically uses a different printing method and material than the press that will produce the piece in high volumes.
A contract proofer typically uses an inkjet printing method whereas high-volume commercial presses use lithographic (offset) or flexographic printing methods. There are also toner-based digital printers that can be used for both proofing and production. Inkjet printers spray ink onto specialized stocks compatible with inkjet technology. Lithographic and flexographic presses use a series of rollers to transfer ink to paper. Inkjet proofers typically use 6 to 11 colors to produce full-color images. A lithographic press usually uses only 4 colors–cyan, magenta, yellow, and black–to produce full-color images. These different methods of production naturally result in differences in color, finish, and capability. The type of paper also plays a roll in the color that will be produced. A gloss sheet will have vibrant, high-contrasting color, and an uncoated sheet will have lighter, more muted colors. The challenge is both targeting each piece of equipment to a given standard (or to each other) and hitting that target with consistency.
We accomplish this by first fine-tuning the prepress and press operations including PDF workflow, CtP calibration, plate linearization, ink consistency, press consumables, press mechanics, and press operation consistency. If the process and elements involved in producing color is constantly changing then it does no good to hit a given target when the starting point could be different from day to day. Much like leveling a house on an unstable foundation. Once this process is stable with an established baseline we use a combination of dot gain curves and ICC profiles to adjust the color. Color charts with thousands of patches are scanned and analyzed to create ICC profiles. This process usually takes several rounds to get the printed result off press to a G7 colorspace standard. A similar process is then applied to the proofer and digital presses. There are two ways to go at matching the proofer to the press. One could use the output of the press as the target for the proofer. This would tend to be more accurate within a company for a given press, but could result in the proofer having a higher Delta E than it could achieve for the standard target. It would also isolate that company’s color to its press as opposed to meeting a global standard. Another way is to use the same G7 standard as the target for the proofer. As long as the press is able to achieve a low Delta E for the same target then this would allow the press and proofer to rely on each other as a common reference with the proofer having the lowest Delta E possible for the standard target. There are different standards for coated and uncoated papers and coincidentally separate processes to achieve and/or simulate the color standard on each.
There are different proofing stocks for inkjet printers for simulating coated versus uncoated products. Coated stocks will have a glossy surface and uncoated (typically called matte for inkjet media) will have a rougher non-glossy surface. One element that limits an ICC’s ability to simulate color between the proof and press is the base white point of the proofing stock. This is measured in whiteness, which is a paper’s ability to reflect all colors equally under D65 lighting conditions, and brightness, which is the amount of blue light the stock reflects. Brightness is also affected by the amount of optical brightening additives in the paper, which can make the paper appear bluer. It is important that the white point of the proofing stock be as close as possible to the white point of the offset stock. This establishes a comparable base between the two media and allows the proofer to more closely simulate the full color gamut of the press.
Phillips Printing uses an 11-color inkjet proofer to produce contract proofs that very closely simulate the color we can achieve with our offset presses on both coated and uncoated stocks. Our offset press, proofer, and digital presses all meet an Idealliance colorspace standards. Setting our clients expectations at the proofing stage has proven to be a valuable asset by greatly limiting any surprises with the finished product. It also allows us to fine tune graphics with accuracy to make sure our clients get what they want. To learn more about proof-to-print and G7 grayscale/colorspace certifications visit idealliance.com or contact us.
