Prepress proofing
Encyclopedia
A Contract Proof usually serves as an agreement between customer and printer and as a color
reference guide for adjusting the press before the final press run. Most contract proofs are a Prepress Proof.
The primary goal of 'proofing' is to serve as a tool for customer verification that the entire job is accurate. Prepress
proofing (also known as off-press proofing) is a cost effective way of providing a visual copy without the expense of creating a Press Proof. If errors are found during the printing
process on press it can prove very costly to one or both parties involved.
Press time is the most expensive part of print media. The main objective of proofing is to produce either a soft or hard copy of what the final product will look like on press. Hard copy proofing usually involves ink-jet printing
or other technologies (i.e. Laminate Proof) to produce high-quality one-off copies of the production artwork. Soft proofing usually involves highly color accurate wide-gamut
computer displays.
"The printed proof is a dispassionate simulation of the ultimate output - a CMYK press sheet. The mission of a proofing system is to create accurate predictions, not pretty pictures." In the best conditions the proofing process will actually try to emulate the effects of the printing press
through color management
and screening techniques, which can be quite challenging because proofing devices may behave and operate quite differently than press devices.
In the late 1940s the first overlay systems were developed. These system produce each of the process colors on a separate sheet of clear film and then register them together to view the final proof.
The Ozalid division of General Aniline and Film Corporation created Ozachrome as the first commercial system used in proofing. Diazo (light sensitive dye) coatings on film were used for each of the process colors and the films were developed using ammonia
vapor. Interestingly, the initial process colors used were red, yellow, blue and black, although other colors may have been used in subsequent years. A black separation was processed on a white paper, while the remaining separations were processed on clear cellulose acetate
.
Around 1965 3M
invented an overlay system called Color Key. Basically sheets of clear polyester were coated with UV sensitive pigmented emulsions in the four process colors, cyan, magenta, yellow and black. Later spot colors were created (Color Key Custom Colors). The sheets were exposed to the artwork via a carbon arc lamp, washed with water and process chemicals, then dried.
As of 2010 overlay proofs are still created, for example for small single drum presses where each color has to be a separate run. Such proofs are usually made using either inkjet printer
s or lamination devices.
Internal (single-sheet) or laminate
systems attempt to overcome the problems with overlay systems by putting all process colors on a single sheet of media. After the end of World War II the first commercial system, called Watercote, was introduced by the Direct Reproduction Corporation.
By the 1970s 3M
developed Transfer Key technology which used a cold lamination adhesive process. Successive layers of colored adhesive would be pressed on the substrate, exposed and washed away until all the colors existed on a single substrate. This later evolved into the Match Print product which used a thermal transfer lamination process. The Match Print trade mark has since been sold to Kodak which uses it today in its MATCHPRINT InkJet and MATCHPRINT Virtual products. Both Color Key and Match Print have also become generic names for types of prepress proofs. Later other similar water process products such as DuPont
Waterproof came on the market.
Later in the 1970s toner based solutions such as Dupont Cromalin were developed.
By the 1980s custom colors, including while and metallics such as gold and silver were becoming common place.
By 1987 the first Iris printer
was commercialized. This was a continuous stream inkjet printer
that was later followed by the Veris printer
in 2004. Initially these printers had unparalleled quality in inkjet printing, but steady advances in drop-on-demand printers has made their quality acceptable to more and more prepress
shops. As of 2010 both Iris and Veris devices are still in use.
In the early 1990s Dye Sublimation was introduced with products like 3M
Rainbow and Kodak DCP9000 and DCP9500.
Also in the early 1990s Laser Sublimation systems were introduced. Products such as the Fuji FINALPROOF, and Kodak Approval
are still in use today.
In the late 1990s laser thermal transfer was developed. These systems are still in use such as the Creo
(now Kodak) Spectrum. The Spectrum was notable in that the same platesetter
device used to make plates was also used to make proofs, resulting in proofs with identical screening as the press.
By 2005 the first spectrophotometers were integrated with inkjet printers, such as the Creo
Veris and HP 2100. By 2009 Epson released a printer with an integrated spectrophotometer. This eliminates much of the labor involved in calibrating the proofing system and validating the proofs by automating the measurement process. However, it slows down overall throughput of the proofing device, so more proofing devices are needed to maintain throughput.
By 2003 soft proofing emerged using well calibrated and profiled computer displays under highly controlled viewing conditions. This approach continues to gain in popularity due to the much lower cost and lesser production time than producing a hard copy proof.
As of 2010 the majority of hard copy contract proofing is done on inkjet and laminate devices, and soft proofing continues to gain in popularity.
Since the late 1990s a number of software proofing solutions developed where the vendors relied upon 3rd party output devices such as Canon, Epson, HP, etc. inkjet printers. Companies include EFI, GMG, Creo
(now Kodak), CGS, Serendipity Software, etc. Previously proofing systems were typically a complete solution from one vendor, but as software has become the dominate enabling technology in proofing, customers enjoy the benefits of being able to use commodity print devices over special proofing devices.
Usually soft proof is done in software applications in combination with color management systems. The monitor used for soft proofing has to be calibrated
, so that the image on the screen looks like the image on the paper. The major problem is the difference of color spaces (RGB in monitor and CMYK in print) and it is solved by using ICC profile
s for input and output devices. Moreover, colors on a monitor depend not only on its properties, but also on lighting conditions in a room where the image is viewed. Usually lighting is standardized and is close to a daylight (D50).
Soft proofing can be used unlimited number of times and is most useful when editing images and designing layout, but is normally not used as a contract proof.
Blueprint (originated from conventional platemaking) is a copy printed in one color and used for checking and correcting mistakes in contents, imposition layout and completeness of data.
Imposition proof (Layout proof) is similar to blueprint but the copy is printed in color. Imposition proof is usually done with a large-format color inkjet printer
.
Color proof provides the color-reliable/color-true reproduction of the contents of the file intended for printing. Color proof is made with inkjet printer
s or thermal sublimation printers
in combination with powerful color management systems. Proofing is performed in full-size format while in some cases small page format is also acceptable. Color proof serves as a guideline for a printing press operator and usually stands for a contract proof.
Screen Proof (True Proof) is a method of proofing used for simulating a raster structure of the printed image. Performing this proof makes it possible to recognize different raster-dependent effects such as smoothness, grade and range of tonal gradations, and moiré
or rosette patterns.
Several vendors offer special proof systems for creating a screen proof. The proof is produced via color donors and thermal transfer (ablation) onto intermediate carriers or onto the substrate used for the print run. Both systems are imagesetter-like devices with
which the image motifs can be reproduced in every detail including their color, screen definition, and screen angle
s. The true proof systems use color foils that are to be processed in separate units (laminators), transferred from intermediate carriers onto production paper and/or laminated, either to protect the proof or to give it the appearance of the surface structure of production paper.
Press proof is a test print of the data directly in a printing press. This can be the press for the production run or a comparable press (using the same print technology) prepared especially for proof purposes. Short runs of 50 or 100 copies can be produced more cost-effectively than with other color proof processes. The individual proof is, however, hardly economically justifiable.
In many cases it makes sense to align the proof with the press, but in other cases it makes sense to align the press with the proof. Typically you would align the press with the proof when you are trying to achieve a particular industry specification (i.e. Fogra, GRACoL, SWOP, etc.). In situations where you are trying to achieve the best possible color on a particular press, typically to distinguish yourself as a printer, you would define a custom color standard for the press and align your proof with the press.
, which consists of baselining, characterizing and calibrating the proofing process.
A baseline is representation of the output device settings (i.e. paper feed, head alignment, etc.) and associated conditions (i.e. media, ink, screening, etc.). A baseline is created by adjusting device settings under a given set of conditions and running test samples, measuring the samples, readjusting the settings, until the output process is brought to an optimal state. Once optimized, a final set of measurements are made of output samples and this data becomes part of the baseline information.
The baseline is then characterized by outputting ECI or IT8.7/4 test charts (samples of color patches), then the charts are scanned with a spectrophotometer to finally produce a color profile of the baseline.
Over time specific device performance (and other conditions) may vary. Certainly different devices of the same device type will also vary with respect to the baseline data. However it is essential that the proofing system always perform as closely as possible to the original color profile. Calibration is a process of outputting more color charts, measuring them and adjusting the color mapping until system performance is as close as possible to the original baseline and color profile. During calibration device settings may also be changed to achieve an optimal output process and subsequent color match.
In ideal circumstances the printing press will also be characterized and calibrated using similar techniques. When there exists a color profile of the press device and a color profile of proofing device, the best emulation of the press on the proofing device is possible. Doing this accurately requires well controlled and repeatable processes (including calibration) to ensure that the color profiles continue to represent the devices involved.
Proof Validation is another aspect of process control. While calibration only ensures that the proofing system is producing output as close to the baseline as possible, proof validation embeds color charts in the artwork itself to ensure that at the artwork matches an industry color standard or a custom color standard (i.e. a specific press that has been characterized). In short it validates that the proofing system emulates the desired press results accurately.
Often customers want 3 dimensional mock-ups of the actual package. This could be cardboard, metal (i.e. aluminum pop can), glass, plastic, etc. This can be very difficult, or impossible to do effectively using inkjet printers so typically laminate processes such as Kodak APPROVAL or Fuji FINALPROOF are needed so that the proof can be transferred to the preferred packaging materials.
In the case of cardboard cartons an automated cutting & creasing table is useful. Typically Computer Aided Design (CAD) software is used to define the cuts and creases based on the proof geometry and this is fed into the cutting & creasing table software.
Most packaging is printed using Flexography
because it is more versatile over the range of materials used in packaging. However the image quality of flexographic prints is often inferior to offset press, and it is important to simulate the characteristics of the press in the proofs so that customers have realistic expectations for the final packaging. Similarly certain materials, such as corrugated cardboard, add their own characteristics to the image, and these too need to be simulated.
Color
Color or colour is the visual perceptual property corresponding in humans to the categories called red, green, blue and others. Color derives from the spectrum of light interacting in the eye with the spectral sensitivities of the light receptors...
reference guide for adjusting the press before the final press run. Most contract proofs are a Prepress Proof.
The primary goal of 'proofing' is to serve as a tool for customer verification that the entire job is accurate. Prepress
Prepress
Prepress is the term used in the printing and publishing industries for the processes and procedures that occur between the creation of a print layout and the final printing...
proofing (also known as off-press proofing) is a cost effective way of providing a visual copy without the expense of creating a Press Proof. If errors are found during the printing
Printing
Printing is a process for reproducing text and image, typically with ink on paper using a printing press. It is often carried out as a large-scale industrial process, and is an essential part of publishing and transaction printing....
process on press it can prove very costly to one or both parties involved.
Press time is the most expensive part of print media. The main objective of proofing is to produce either a soft or hard copy of what the final product will look like on press. Hard copy proofing usually involves ink-jet printing
Inkjet printer
An inkjet printer is a type of computer printer that creates a digital image by propelling droplets of ink onto paper. Inkjet printers are the most commonly used type of printer and range from small inexpensive consumer models to very large professional machines that can cost up to thousands of...
or other technologies (i.e. Laminate Proof) to produce high-quality one-off copies of the production artwork. Soft proofing usually involves highly color accurate wide-gamut
Gamut
In color reproduction, including computer graphics and photography, the gamut, or color gamut , is a certain complete subset of colors. The most common usage refers to the subset of colors which can be accurately represented in a given circumstance, such as within a given color space or by a...
computer displays.
"The printed proof is a dispassionate simulation of the ultimate output - a CMYK press sheet. The mission of a proofing system is to create accurate predictions, not pretty pictures." In the best conditions the proofing process will actually try to emulate the effects of the printing press
Printing press
A printing press is a device for applying pressure to an inked surface resting upon a print medium , thereby transferring the ink...
through color management
Color management
In digital imaging systems, color management is the controlled conversion between the color representations of various devices, such as image scanners, digital cameras, monitors, TV screens, film printers, computer printers, offset presses, and corresponding media.The primary goal of color...
and screening techniques, which can be quite challenging because proofing devices may behave and operate quite differently than press devices.
History
Since the first days of Johannes Gutenberg proofing has just been press proofs - you make a short run on press to verify what you are going to do on a production run. As technology evolved to lower the per-copy cost of a printing job, the cost of starting a production run continued to rise. Today it can be very costly to start up a production press, and cost prohibitive to run a press proof. While some people may think a press proof is the ultimate proof quality, this is not necessarily so, especially if the production run is done days or weeks later when press conditions may have changed, or the production run is done on a different press than the press proof.In the late 1940s the first overlay systems were developed. These system produce each of the process colors on a separate sheet of clear film and then register them together to view the final proof.
The Ozalid division of General Aniline and Film Corporation created Ozachrome as the first commercial system used in proofing. Diazo (light sensitive dye) coatings on film were used for each of the process colors and the films were developed using ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
vapor. Interestingly, the initial process colors used were red, yellow, blue and black, although other colors may have been used in subsequent years. A black separation was processed on a white paper, while the remaining separations were processed on clear cellulose acetate
Cellulose acetate
Cellulose acetate , first prepared in 1865, is the acetate ester of cellulose. Cellulose acetate is used as a film base in photography, as a component in some adhesives, and as a frame material for eyeglasses; it is also used as a synthetic fiber and in the manufacture of cigarette filters and...
.
Around 1965 3M
3M
3M Company , formerly known as the Minnesota Mining and Manufacturing Company, is an American multinational conglomerate corporation based in Maplewood, Minnesota, United States....
invented an overlay system called Color Key. Basically sheets of clear polyester were coated with UV sensitive pigmented emulsions in the four process colors, cyan, magenta, yellow and black. Later spot colors were created (Color Key Custom Colors). The sheets were exposed to the artwork via a carbon arc lamp, washed with water and process chemicals, then dried.
As of 2010 overlay proofs are still created, for example for small single drum presses where each color has to be a separate run. Such proofs are usually made using either inkjet printer
Inkjet printer
An inkjet printer is a type of computer printer that creates a digital image by propelling droplets of ink onto paper. Inkjet printers are the most commonly used type of printer and range from small inexpensive consumer models to very large professional machines that can cost up to thousands of...
s or lamination devices.
Internal (single-sheet) or laminate
Laminate
A laminate is a material that can be constructed by uniting two or more layers of material together. The process of creating a laminate is lamination, which in common parlance refers to the placing of something between layers of plastic and gluing them with heat and/or pressure, usually with an...
systems attempt to overcome the problems with overlay systems by putting all process colors on a single sheet of media. After the end of World War II the first commercial system, called Watercote, was introduced by the Direct Reproduction Corporation.
By the 1970s 3M
3M
3M Company , formerly known as the Minnesota Mining and Manufacturing Company, is an American multinational conglomerate corporation based in Maplewood, Minnesota, United States....
developed Transfer Key technology which used a cold lamination adhesive process. Successive layers of colored adhesive would be pressed on the substrate, exposed and washed away until all the colors existed on a single substrate. This later evolved into the Match Print product which used a thermal transfer lamination process. The Match Print trade mark has since been sold to Kodak which uses it today in its MATCHPRINT InkJet and MATCHPRINT Virtual products. Both Color Key and Match Print have also become generic names for types of prepress proofs. Later other similar water process products such as DuPont
DuPont
E. I. du Pont de Nemours and Company , commonly referred to as DuPont, is an American chemical company that was founded in July 1802 as a gunpowder mill by Eleuthère Irénée du Pont. DuPont was the world's third largest chemical company based on market capitalization and ninth based on revenue in 2009...
Waterproof came on the market.
In the early 1960's, several attempts were made to develop electrophotographic proofing processes based on the electrofax principle, using paper coated with zinc oxide in a resistive binder as a photoconductor and toners consisting of ink pigments dispersed in liquid Isopar. The electrofax principle was introduced in the United States by RCARCARCA Corporation, founded as the Radio Corporation of America, was an American electronics company in existence from 1919 to 1986. The RCA trademark is currently owned by the French conglomerate Technicolor SA through RCA Trademark Management S.A., a company owned by Technicolor...
. and the use of liquid toners was developed in Australia by Ralph Metcalf and Robert Wright of the Australian government. Other groups worked on similar processes, but never got to market.
Later in the 1970s toner based solutions such as Dupont Cromalin were developed.
By the 1980s custom colors, including while and metallics such as gold and silver were becoming common place.
By 1987 the first Iris printer
Iris printer
An IRIS printer is a large-format color inkjet printer introduced in 1987 by IRIS Graphics of Bedford, Massachusetts and currently manufactured by the Graphic Communications Group of Eastman Kodak, designed for prepress proofing...
was commercialized. This was a continuous stream inkjet printer
Inkjet printer
An inkjet printer is a type of computer printer that creates a digital image by propelling droplets of ink onto paper. Inkjet printers are the most commonly used type of printer and range from small inexpensive consumer models to very large professional machines that can cost up to thousands of...
that was later followed by the Veris printer
Veris printer
The Veris printer is a medium format 1500 DPI color inkjet printer manufactured by the Graphic Communications Group of Eastman Kodak, which is used for digital Prepress proofing. A refinement of the Iris printer, the Veris also uses a continuous flow ink system to produce continuous-tone output on...
in 2004. Initially these printers had unparalleled quality in inkjet printing, but steady advances in drop-on-demand printers has made their quality acceptable to more and more prepress
Prepress
Prepress is the term used in the printing and publishing industries for the processes and procedures that occur between the creation of a print layout and the final printing...
shops. As of 2010 both Iris and Veris devices are still in use.
In the early 1990s Dye Sublimation was introduced with products like 3M
3M
3M Company , formerly known as the Minnesota Mining and Manufacturing Company, is an American multinational conglomerate corporation based in Maplewood, Minnesota, United States....
Rainbow and Kodak DCP9000 and DCP9500.
Also in the early 1990s Laser Sublimation systems were introduced. Products such as the Fuji FINALPROOF, and Kodak Approval
Approval proofer
The Approval proofer, also known as the Approval Digital Imaging System or Kodak APPROVAL System, was designed for use in Prepress proofing, especially for the highest quality contract proofs....
are still in use today.
In the late 1990s laser thermal transfer was developed. These systems are still in use such as the Creo
Creo
Creo, now part of Eastman Kodak Company, was a Burnaby, British Columbia Canada-based company involved in imaging and software technology for computer to plate and digital printing. The name derives from the Latin creo, "I create."...
(now Kodak) Spectrum. The Spectrum was notable in that the same platesetter
Platesetter
A platesetter is a machine which receives a raster image from a raster image processor and in turn, creates a lithographic plate suitable for use on an offset press....
device used to make plates was also used to make proofs, resulting in proofs with identical screening as the press.
By 2005 the first spectrophotometers were integrated with inkjet printers, such as the Creo
Creo
Creo, now part of Eastman Kodak Company, was a Burnaby, British Columbia Canada-based company involved in imaging and software technology for computer to plate and digital printing. The name derives from the Latin creo, "I create."...
Veris and HP 2100. By 2009 Epson released a printer with an integrated spectrophotometer. This eliminates much of the labor involved in calibrating the proofing system and validating the proofs by automating the measurement process. However, it slows down overall throughput of the proofing device, so more proofing devices are needed to maintain throughput.
By 2003 soft proofing emerged using well calibrated and profiled computer displays under highly controlled viewing conditions. This approach continues to gain in popularity due to the much lower cost and lesser production time than producing a hard copy proof.
As of 2010 the majority of hard copy contract proofing is done on inkjet and laminate devices, and soft proofing continues to gain in popularity.
Since the late 1990s a number of software proofing solutions developed where the vendors relied upon 3rd party output devices such as Canon, Epson, HP, etc. inkjet printers. Companies include EFI, GMG, Creo
Creo
Creo, now part of Eastman Kodak Company, was a Burnaby, British Columbia Canada-based company involved in imaging and software technology for computer to plate and digital printing. The name derives from the Latin creo, "I create."...
(now Kodak), CGS, Serendipity Software, etc. Previously proofing systems were typically a complete solution from one vendor, but as software has become the dominate enabling technology in proofing, customers enjoy the benefits of being able to use commodity print devices over special proofing devices.
Proofing methods
Depending on the quality needed and the use of product there are two major types of proof:- soft proof;
- hard proof;
Soft proof
Soft proof describes the simulation of the print result on a monitor. This is the cheapest solution for proofing since no additional equipment, except a monitor, is needed.Usually soft proof is done in software applications in combination with color management systems. The monitor used for soft proofing has to be calibrated
Color calibration
The aim of color calibration is to measure and/or adjust the color response of a device to a known state. In ICC terms this is the basis for a additional color characterization of the device and later profiling. In non ICC workflows calibration refers sometimes to establishing a known relationship...
, so that the image on the screen looks like the image on the paper. The major problem is the difference of color spaces (RGB in monitor and CMYK in print) and it is solved by using ICC profile
ICC profile
In color management, an ICC profile is a set of data that characterizes a color input or output device, or a color space, according to standards promulgated by the International Color Consortium...
s for input and output devices. Moreover, colors on a monitor depend not only on its properties, but also on lighting conditions in a room where the image is viewed. Usually lighting is standardized and is close to a daylight (D50).
Soft proofing can be used unlimited number of times and is most useful when editing images and designing layout, but is normally not used as a contract proof.
Hard proof
Hard proof is an actual printed sample of a printed product. It is further divided into five general classificationsBlueprint (originated from conventional platemaking) is a copy printed in one color and used for checking and correcting mistakes in contents, imposition layout and completeness of data.
Imposition proof (Layout proof) is similar to blueprint but the copy is printed in color. Imposition proof is usually done with a large-format color inkjet printer
Inkjet printer
An inkjet printer is a type of computer printer that creates a digital image by propelling droplets of ink onto paper. Inkjet printers are the most commonly used type of printer and range from small inexpensive consumer models to very large professional machines that can cost up to thousands of...
.
Color proof provides the color-reliable/color-true reproduction of the contents of the file intended for printing. Color proof is made with inkjet printer
Inkjet printer
An inkjet printer is a type of computer printer that creates a digital image by propelling droplets of ink onto paper. Inkjet printers are the most commonly used type of printer and range from small inexpensive consumer models to very large professional machines that can cost up to thousands of...
s or thermal sublimation printers
Dye-sublimation printer
A dye-sublimation printer is a computer printer which employs a printing process that uses heat to transfer dye onto medium materials such as a plastic card, paper, or fabric. The sublimation name is applied because the dye transitions between the solid and gas states without going through a...
in combination with powerful color management systems. Proofing is performed in full-size format while in some cases small page format is also acceptable. Color proof serves as a guideline for a printing press operator and usually stands for a contract proof.
Screen Proof (True Proof) is a method of proofing used for simulating a raster structure of the printed image. Performing this proof makes it possible to recognize different raster-dependent effects such as smoothness, grade and range of tonal gradations, and moiré
Moiré pattern
In physics, a moiré pattern is an interference pattern created, for example, when two grids are overlaid at an angle, or when they have slightly different mesh sizes.- Etymology :...
or rosette patterns.
Several vendors offer special proof systems for creating a screen proof. The proof is produced via color donors and thermal transfer (ablation) onto intermediate carriers or onto the substrate used for the print run. Both systems are imagesetter-like devices with
which the image motifs can be reproduced in every detail including their color, screen definition, and screen angle
Screen angle
In offset printing, the screen angle is the angle at which the halftones of a separated color is outputted to a lithographic film, hence, printed on final product media.-Why should screen angles differ:...
s. The true proof systems use color foils that are to be processed in separate units (laminators), transferred from intermediate carriers onto production paper and/or laminated, either to protect the proof or to give it the appearance of the surface structure of production paper.
Press proof is a test print of the data directly in a printing press. This can be the press for the production run or a comparable press (using the same print technology) prepared especially for proof purposes. Short runs of 50 or 100 copies can be produced more cost-effectively than with other color proof processes. The individual proof is, however, hardly economically justifiable.
Issues
Proofing can either be viewed subjectively as an art based on training, experience, talent and judgment; or objectively as a science based on measurement, algorithms, and analysis; but in practice it is somewhere in between. Increasingly, however, printers rely on scientific methods as it is often more cost effective to buy the necessary technology than to acquire, train and retain skilled artisans.In many cases it makes sense to align the proof with the press, but in other cases it makes sense to align the press with the proof. Typically you would align the press with the proof when you are trying to achieve a particular industry specification (i.e. Fogra, GRACoL, SWOP, etc.). In situations where you are trying to achieve the best possible color on a particular press, typically to distinguish yourself as a printer, you would define a custom color standard for the press and align your proof with the press.
Process Control
A central aspect of scientific proofing is process controlProcess control
Process control is a statistics and engineering discipline that deals with architectures, mechanisms and algorithms for maintaining the output of a specific process within a desired range...
, which consists of baselining, characterizing and calibrating the proofing process.
A baseline is representation of the output device settings (i.e. paper feed, head alignment, etc.) and associated conditions (i.e. media, ink, screening, etc.). A baseline is created by adjusting device settings under a given set of conditions and running test samples, measuring the samples, readjusting the settings, until the output process is brought to an optimal state. Once optimized, a final set of measurements are made of output samples and this data becomes part of the baseline information.
The baseline is then characterized by outputting ECI or IT8.7/4 test charts (samples of color patches), then the charts are scanned with a spectrophotometer to finally produce a color profile of the baseline.
Over time specific device performance (and other conditions) may vary. Certainly different devices of the same device type will also vary with respect to the baseline data. However it is essential that the proofing system always perform as closely as possible to the original color profile. Calibration is a process of outputting more color charts, measuring them and adjusting the color mapping until system performance is as close as possible to the original baseline and color profile. During calibration device settings may also be changed to achieve an optimal output process and subsequent color match.
In ideal circumstances the printing press will also be characterized and calibrated using similar techniques. When there exists a color profile of the press device and a color profile of proofing device, the best emulation of the press on the proofing device is possible. Doing this accurately requires well controlled and repeatable processes (including calibration) to ensure that the color profiles continue to represent the devices involved.
Proof Validation is another aspect of process control. While calibration only ensures that the proofing system is producing output as close to the baseline as possible, proof validation embeds color charts in the artwork itself to ensure that at the artwork matches an industry color standard or a custom color standard (i.e. a specific press that has been characterized). In short it validates that the proofing system emulates the desired press results accurately.
Proofing for Packaging
Producing proofs for packaging faces a number of challenges beyond those for conventional offset press.Often customers want 3 dimensional mock-ups of the actual package. This could be cardboard, metal (i.e. aluminum pop can), glass, plastic, etc. This can be very difficult, or impossible to do effectively using inkjet printers so typically laminate processes such as Kodak APPROVAL or Fuji FINALPROOF are needed so that the proof can be transferred to the preferred packaging materials.
In the case of cardboard cartons an automated cutting & creasing table is useful. Typically Computer Aided Design (CAD) software is used to define the cuts and creases based on the proof geometry and this is fed into the cutting & creasing table software.
Most packaging is printed using Flexography
Flexography
Flexography is a form of printing process which utilizes a flexible relief plate. It is basically an updated version of letterpress that can be used for printing on almost any type of substrate including plastic, metallic films, cellophane, and paper...
because it is more versatile over the range of materials used in packaging. However the image quality of flexographic prints is often inferior to offset press, and it is important to simulate the characteristics of the press in the proofs so that customers have realistic expectations for the final packaging. Similarly certain materials, such as corrugated cardboard, add their own characteristics to the image, and these too need to be simulated.
See also
- Online artwork proofing, feedback, review and approval toolOnline artwork proofing, feedback, review and approval toolAn Online artwork proofing, feedback, review and approval tool is a web-based Collaborative software that helps studios with internal and client communication.-How it works:...
- Online proofingOnline proofingOnline proofing is the process undertaken by web designers, photographers, marketing agencies and video production companies, among others, to automate the review and approval of work online...
- Press check (printing)