SWOP WEBOFFSET AND GRAVURE SPECIFICATIONS - 9th EDITION
Viewing of Artwork and Proofs
* Artwork, proofs and final printed product MUST be viewed and/or compared using 5000 Kelvin (D50) illumination complying with ISO 3664:2000, "Viewing conditions for graphic technology and photography," with the exception noted below.
* Following this viewing standard is now more important than ever due to increased use of different dyes and pigments for proofing. Viewing booth manufacturers can provide compliance information.
* SWOP specifies that when viewing SWOP proofs or printed signatures the backing under the proof should consist of at least five sheets of the same substrate material. Note: This viewing condition deviates from that specified in the ISO 3664 P1 conformance level, which states that a black backing should be used when viewing proofs and printed signatures.
Digital Page Preparation
* SWOP assumes that, as of the publication of this booklet, all pages are created by digital means, whether they are to be delivered as film or digital file. Previously, this section was captioned "Film Preparation." Many publications are now requesting the page to be delivered in digital form. We will address both forms of delivery.
* A content proof made from the supplied digital file must be furnished to the Prepress Service Supplier with all supplied digital files.
* What is important is that the printed results should meet the customer's expectations for quality reproduction whether the page is produced from film or a digital file. Type Reproduction
* Thin lines, fine serifs and medium or small type should be restricted to one color. Reproduce all colored type with a minimum of colors.
* Reverse type and line art should not be less than .007" (1/2 point rule) at the thinnest part of a character or rule. Reverse type should use the dominant color (usually 70% or more) for the shape of letters. Where practical, and not detrimental to the appearance of the job, make the type in subordinate colors slightly larger to minimize register problems on the production press. Small type and fine serifs should not be used for reverse type. The surrounding tone must be dark enough to ensure legibility. See section below on "Image Trapping."
* Overprinted (surprinted) type should not be less than .004" (1/3 point rule) at the thinnest part of a character or rule. When type is to be overprinted, the background should be no heavier than 30% in any one color and no more than 90% total in all four colors for legibility.
* All supplied materials sent to the publisher or printer must be properly trapped and, when possible, the image trapping should be represented in the accompanying SWOP proofs.
* Overlap of colors should be introduced when line work abuts line work, or abuts continuous tone images, with the dominant colors providing the image shape. Lighter colors should be spread into darker colors. This overlap should be sufficient to minimize register problems on production presses.
* Since files must be trapped when exchanging PDF/X-1 files, the trap flag must be set to "TRUE." Vignette or Fadeaway Edges/ Minimum Printable Dot (Minimum Tone Value)
* Special care should be taken with fadeaway edges where the fadeaway is made up of more than one color. In many cases, fadeaway shadows are best reproduced in black only.
* For film, the exposure process will determine the smallest film dot that can be effectively reproduced on plate. This is typically 2% for plates requiring negative film and 4% for plates requiring positive film. It is important to prepare input material, including proofs, with these limits in mind.
* With computer-to-plate it is possible to accurately produce 1% dots on plate. In preparing digital files this should be kept in mind. For critical work it is important to use a proofing system that reflects this minimum tone reproduction characteristic.
* Although developments in digital plating and engraving technologies have improved tone reproduction control in the extreme highlights (less than a 5% dot), designers should still be cautious in placing image components in this tonal range. This is because all-digital production is not yet universal and process control cannot always guarantee precise reproduction below a 5% dot, depending on the process involved. This caution may be relaxed in situations where appropriate agreement has been made among all parties in the production process.
* The gravure process has similar requirements. For additional information on gravure requirements see page 23 in the current SWOP booklet.
* 133 lines per inch (52 lines per centimeter) is the recommended nominal screen ruling.
* Screen rulings coarser than 133 lines per inch may not be acceptable for gravure publications.
* For black-and-white reproduction, check individual publisher for screen ruling requirements.
* The use of finer screen rulings and stochastic or other alternative screening must be pre-approved by the publisher and printer.
* Digital files sent to the publication printer should not include screening parameters and dot shape.
* Whoever generates film or plates from digital files must follow the specification shown below.
* The screen angles of the colors should be 30 degrees apart, with the yellow placed 15 degrees from the other colors and between the cyan and magenta or the cyan and black. It is possible to place the yellow on the same angle as the cyan or, depending on the dominant colors in the picture, on the same angle as the magenta. This alignment has the advantage of spacing all the angles by 30 degrees and eliminating the moiré that often occurs between yellow and the other colors.
* It is desirable to have the dominant color (normally magenta) on the 45 degree angle. When significant Gray Component Replacement (GCR) is used, and if black becomes the dominant color, black should be printed at the 45 degree angle instead of magenta.
* Screen angles for two-color printing should follow the same guidelines, with the black at 45 degrees.
* Screen angles and rulings should be such that no moire pattern should appear in the film, proof or print.
* If the advertiser/agency desires to specify screening requirements to the printer, it must be done with prior agreement with all parties involved. In computer-to-plate workflow the responsibility for meeting the customer's screening requirements lies with the plate-maker/printer. The printer is responsible for reporting moire to the publisher or advertiser/agency and to help resolve the problem.
* Normally gravure printers require digital files and not film; however, if film were to be sent to a gravure printer, colors other than yellow should avoid angles between 75 degrees and 105 degrees. Gray Balance
* Good visual gray balance, under standard viewing conditions, is essential to proper four-color printing.
* In order to reproduce black, the undercolors should be in a neutral or gray balance.
* It is important to coordinate and control the gray balance of the separations with the gray balance in proofing and printing. The tint values that produce gray balance in SWOP proofing are listed in the Proofing Section, page 18.
Total Area Coverage (TAC): Undercolor Removal (UCR) and Gray Component Replacement (GCR)
* The total of dot percentages in any spot in the four-color file or films should be no more than 300%.
* For some small, non-critical image areas of a picture that carry no significant detail, TAC may exceed 300%. TAC in these small image areas must be less than 325 %.
* When GCR is used, it is important to add color back under blacks to maintain gloss and density. Recommended total area coverage as a function of black dot area percentage is shown in the table on page 35. This is accomplished by the use of Under Color Addition (UCA). Percentages of tones in film should be read with a properly calibrated transmission densitometer.
* In two-color printing, Undercolor Removal (UCR) is not usually necessary, as long as the two inks are trapping properly. It is probably advantageous that only one color be solid. For the discussion of TAC on Super Calendared (SC) paper see page 29 in the current SWOP booklet.
Digital Files Requirements
* Files representing print-ready material should be exchanged only as CMYK data using the TIFF/IT-P1 or PDF/X-1 file formats or their future versions. The use of non-standard, application or native file formats is not permitted.
* A SWOP proof, made from the supplied file, must be furnished to the publication printer with all supplied digital files.
* The files should include all image trapping and should incorporate all of the other logical parameters specified by SWOP for film preparation (e.g., UCR/GCR, gray balance, register marks, total area coverage, etc.). However, files should not include screening parameters or dot shape. When plates or film are made by the printer directly from digital files, it is the printer's responsibility to report more pattern problems to the agency and publisher and to help them resolve the problems whenever possible. Multiple sets of files and proofs may be necessary with multiple insertion orders, depending on the requirements of the individual publisher.
* File resolutions should conform to, or be compatible with, the publication printer's output device resolution requirements. The individual publisher should be consulted for this information.
* Data compression used within files should comply with the provisions of the TIFF/IT-P1 and PDF/X-1 file format standards. Data compression applied to the complete file structure should only be used if the sender and receiver agree to the method and use of file compression. Only lossless compression should be used, defined as a method of compression that results in no (0%) data alterations to the reconstructed file. It is the sender's responsibility to ensure that the publisher and/or the printer is aware of the type of compression used and has the means to decompress the file. Other types of compression may be acceptable in the future, as PDF/X gains acceptance and more implementations become viable.
* SWOP recognizes the DDAP User Requirement Specification regarding editability. In the event that changes need to be made, they should only be made at the direction of the agency/advertiser, with agreement of the publisher and printer.
* The method of delivery (e.g., magnetic tape, removable disk, electronic transmission) and file formats to be used for exchange of digital files should be agreed to by all participants.
* In the future, digital files may be accompanied by either an electronic job ticket or ad copy instructions, potentially utilizing XML. Business information as detailed in IDEAlliance Standard 144 - 2000, such as insertion orders, space reservation and ad copy instructions, may be transmitted using this framework. Information is available from IDEAlliance.
Final Film Physical Properties
* All film should be dimensionally stable and of identical thickness (0.004 inch is recommended).
* Film should be supplied in one piece per color and identified by color and kind (e.g., "black positive").
* Film should be hard dot. No camera or etched film is acceptable. Film produced by imagesetters is acceptable.
* All opaquing should be done on the non-emulsion side of the film and should be minimal. * The clear area (Dmin) of the film should have a density of no more than 0.07.
* The black area (Dmax) of the film should have a density of no less than 3.50.
* Gravure publications require type to be provided on separate films.
* All film should be looked at as "right-reading."
* Information on whether emulsion side should be "up" or "down," and whether film should be "negative" or "positive," should be obtained from the publisher.
* Film for color ads should have four centered register marks identical in each color located approximately 1/2 inch outside the "live" area of the ad. Where ads are less than full page (non-bleed) it may be necessary for the printer to remove the register marks before plating. Any removal of register marks required for page form assembly is the responsibility of the printer.
* Register marks should include solid lines at least 1/4" long on both axes.
* The lines should be precisely the same width (thickness) in each color. Multiple Insertion
* The publisher's specified number and kind of film sets, along with the required proofs, should be supplied.
* Appropriate process control elements should be used in contacting this final film to ensure that all are identical and accurate reproductions of the master files or films. Examples are the GATF Plate Control Target, UGRA/FOGRA Plate Control Wedge and the RIT Microline Resolution Target.
* Appropriate process control elements should also be used in the digital output of final films to ensure that all are identical and accurate reproductions of the master files.
* The color guide should be an offset press proof made to SWOP specifications, or an off-press proof made according to the manufacturer's SWOP Application Data Sheet using a SWOP Certified Proofing System.
* All proofs must contain a color control bar in order to be considered an acceptable SWOP proof and be clearly marked with available job information and proofing system identification.
* All color proofs should be in exact register.
* Proofs can change over time. They should be dated and not used if it is known that a change in appearance has occurred. (e.g., exposure to light, over time, will affect the color accuracy of a proof.)
Proofs made from separation film materials should use an original, hard-dot film control bar. Proofs made using digital proofing systems should use a digital control bar having similar content to the hard-dot film control bar.
This color control bar should have the following characteristics:
* Screened areas with rulings of 133 lines per inch with tint values of 25%, 50% and 75% of each of the primary colors in physical proximity to a solid patch. Two-color overprints of the same 25%, 50% and 75% are also recommended. Additional areas such as 1%, 2%, 3%, 5% and 95%, 97%, 98%, 99% may be useful, especially for digital output.
* A gray balance bar must be included on the proof designed to match the neutral appearance and weight of black tints of three different values, under standard viewing conditions.
* The three-color gray balance portion of the color bar should have the following values.
Black Cyan Magenta Yellow 75% 75% 63% 63% 50% 50% 39% 39% 25% 25% 16% 16%
Note: Use only the original films as supplied by the manufacturer for exposing the control bars. Contacting or duplicating this film will lead to aberrations in sensitive areas and is unacceptable.
Computer-to-Plate (CTP) digital control bars should include the above general characteristics but may require additional features for controlling digital plate systems. Two-Color and Black-and-White Proofing
A press proof or off-press proof should be furnished with each black-and-white or two-color file or film set delivered. A photographic print of the black film with a color overlay may be acceptable to certain publications. Check individual publishers for specifications regarding acceptability of proofs, screen ruling and number of proofs required.
The press proof or off-press proof should be accompanied by a cover sheet or label which includes the name, address and phone number of the prepress service supplier and, if possible, the name of the person or persons who should be contacted in case of a problem.
The individual publisher should specify the number of proofs required.
Proofs should not be stapled or otherwise damaged in any area that might interfere with the densitometer reading of the color bars.
All proofs should match one another and be consistent in color and tone reproduction.
Press Proofing Inks Standard Ink Colors
Proofing inks that conform to the color specifications of the SWOP/NAPIM Official Reference Process Inks must be used. These same inks have undergone extensive testing as part of the international standards development of ISO 2846-1 (Euroscale) and have been shown to be very similar to inks made to this same standard in Europe and Japan.
For availability of proofing ink samples and for information on the voluntary verification program, see the General Reference Section on page 42. Standard Second Colors x Yellow (SWOP process yellow) x Blue (SWOP process cyan) x SWOP Red x SWOP Green
SWOP Red and SWOP Green are equivalent to, and can be proofed as, solid over-prints of magenta/yellow and cyan/yellow respectively.
Matched Colored Inks
Matched colored inks other than standard second-color inks are often used, depending on the availability of open press cylinders. Arrangements must be made with the publisher in advance in order to run matched colors.
Standard proofing paper is 60# basis weight paper of 72 (nominal) TAPPI brightness. Brightness will vary with age.
The paper may be a coated groundwood stock or a sheet coated to simulate the appearance of such a groundwood stock. A paper known to meet these specifications is Textweb Proofing Paper, manufactured by Deferiet Paper Company (see page 41) and sold in sheet form by various paper merchants. Other papers meeting the technical specifications shown on page 41 in the current SWOP booklet may be used.
Press proofing should be done on a (minimum) four-color press with the ad or editorial page printing in the same direction as in the eventual press run.
The sequence of KCMY is recommended (but not specified) for SWOP press proofing. Sequence can have an affect on color balance depending on the ink's transparency and ink trapping properties. It should be noted that SWOP Certified Press Proofs are prepared using the sequence of KCMY.
To achieve proper color reproduction particular attention should be paid to solid ink density, ink trap, tone value increase (dot gain), gray balance, doubling and other four-color print characteristics. The gray balance elements incorporated in the standard proofing bars are the most effective devices for checking on these aspects of proof-press performance.
Proofer's Color Bars
Proofs should carry a color control bar stripped in register, positioned perpendicular to the direction of printing and covering the full width of the image area. Proofs made from separation film materials should use an original, hard-dot film control bar, as specified in "Color Bars" under "Proofing," on page 18.
This color control bar should have the following characteristics:
A repeating pattern of solids of individual inks, and two-color and three-color overprints as specified under "Color Bars" under "Proofing," on page 18.
Target areas visually sensitive to slur and tone value increase/dot gain.
A gray balance bar must be included on the proof, which has three-color tints running parallel to, and designed to match the neutral appearance and weight, of black tints of three different values, under standard viewing conditions.
Film material and digital control bars as described above may be obtained from GATF. Specify: "GATF/SWOP Proofing Bar" for film and "GATF/SWOP Digital Proofing Bar" for digital output. Control bars containing the specified characteristics may also be created by the user or obtained from other sources.
Solid Ink Density and Color References
SWOP Specifications recommend the use of Status T densitometers for measuring process control parameters such as density, Tone Value Increase (Total Dot Gain) and Print Contrast. Solid-color verification and control can be achieved using either Status T densitometry (absolute density) or colorimetric measurement in accordance with CGATS.4 and CGATS.5 along with the proper use of the SWOP Color References.
Ink density and color in proofing should be controlled by the use of the SWOP Hi-Lo Color References.
Proofers should control ink density so that the density values on dry proofs fall between the Hi and Lo references. SWOP no longer supplies a single color reference.
The SWOP Hi-Lo Color References are printed on SWOP specified paper using SWOP proofing inks. These inks have been verified as being accurate in color by the SWOP/NAPIM Proofing Ink Verification Program. The SWOP Hi-Lo Color References are available on a subscription basis from the International Prepress Association, 552 W. 167th Street, South Holland, IL 60473; 708-596-5110. These provide physical references for both density and color measurement. See page 43.in the current SWOP booklet.
Tone Value Increase (Total Dot Gain)
In order to ensure properly balanced tone reproduction, Tone Value Increase (Total Dot Gain) at 50% from file or film to print should be:
Target Value Tolerance ±3% Yellow 18% 15-21% Magenta 20% 17-23% Cyan 20% 17-23% Black 22% 19-25%
# In order to help obtain proper gray balance, included in this specification is the restriction that gain values of the three colors (Y, M, C) should not differ from each other by more than 4% from their target value. For example: if either cyan or magenta is +2% (22%), in dot gain, yellow deviation should not be greater than -2% (16%).
Target Value Example From Target Yellow 18% 16% -2% Magenta 20% 20% 0% Cyan 20% 22% 2%
# Another way to explain this specification is: after adding two percentage points to the measured yellow dot gain value, process colors (Y, M, C) should not differ by more than four percentage points.
# Print Contrast is an important characteristic in printing and proofing and should be controlled in order to better define the entire tone curve.
# As of this edition of SWOP, Print Contrast at the 75% tone value is a specification for proofing and must be maintained.
# Print Contrast specifications at the 75% tone value are based on data obtained from the several Certified Press runs are as follows:
# Color Center Point and Range Yellow 25±5% Magenta & Cyan 35±5% Black 38±5%
# Adherence to both the lower and upper tolerance levels is important because deviation from either would indicate problems with the highlight or shadow portions of the tone scale. See page 47 for information about calculating Print Contrast.
# Since 1996, SWOP has approved the use of off-press proofs.
# As of this edition, SWOP is specifying the use of ONLY those off-press proofing systems which have been Certified by SWOP. These systems have been shown capable of producing a proof that closely matches a SWOP Certified Press Proof. This certification program is outlined below.
# Directions for producing proofs from these systems are contained in the manufacturers' Application Data Sheets (ADS). The Application Data Sheet presents the manufacturer's recommendations including sequence, colorants and substrate, which when followed, result in appropriate colorimetric (CIELAB) and densitometric (density and TVI) data that provide the best match to SWOP Certified Press Proofs.
# These ADS's are available on the SWOP web site at http://www.swop.org under the links, " SWOP Certification" and then, Certified Application Data Sheets". The proofing system operator is responsible for following the appropriate SWOP Application Data Sheet (ADS) and verifying conformance by measurement of the appropriate color bar to the specific ADS values.
# ANSI/CGATS TR 001, documents the colorimetric characterization of the CMYK to CIELAB relationship for print conditions that are used to produce SWOP certified press proofs. SWOP specifies the use of ANSI/CGATS TR 001 characterization for any color-managed applications (e.g., SWOP certified off-press proofing, remote proofing, etc.) SWOP Off-Press Proofing Certification Program
# For many years, representatives of the major off-press proofing manufacturers have known and demonstrated that their proofing systems could match one another and could come close to matching a Certified Press Proof. Problems in the industry stemmed from both vendors and users misusing or changing the results of the proofs based on their own biases and applications.
# In 1996, at the request of the major proofing manufacturers, the SWOP Technical Committee convened the Off-Press Proofing Task Force to look into a way that SWOP might certify the systems for the use of their customers. That Certification Program is now in place. See SWOP Certification on page 47 in the General Reference Section.
# All off-press proofs should include a color bar as specified in "Color Bars" under "Proofing" on page 18, to be acceptable SWOP proofs. This color bar could take the form of a manufacturer's color control guide, a GCA/GATF Proof Comparator, a SWOP bar available on the SWOP website, or a GATF/SWOP Proofing Bar or their digital equivalents. An exposure control element may also be included where appropriate.
# If the user is unable to verify conformance to the manufacturer's ADS or there is an obvious mismatch to a SWOP Certified Press Proof, the manufacturer should be contacted for corrective action.
# Fully processed samples of actual off-press proofs using a SWOP Calibration Kit, containing color pictures and a SWOP approved control bar may be sent by users to the SWOP Color Laboratory for verification. Information on how to obtain a SWOP Calibration Kit can be found on the SWOP web site at http://www.swop.org or by E-mail to email@example.com
# Submitted proofs will be compared visually and instrumentally for SWOP conformance to data contained in the manufacturer's Application Data Sheet (see sample on page 53) and a report will be generated. A fee will be charged for measurement, analysis and reports issued.
GAA Input Specifications for Publication Gravure
* GAA input specifications for publication gravure digital files are virtually identical to the SWOP specifications outlined in this booklet. Today, many publications successfully utilize both printing processes in the production of their magazines. Advertisers who place ads in these publications expect both processes to match their supplied SWOP proof.
* Listed below are a few areas where the GAA feels that additional information may be useful in helping suppliers prepare input for gravure publications.
* The GAA fully supports and has been actively involved in the development of industry standards for the exchange of digital data files for advertisements. The GAA has worked closely with CGATS, ANSI and ISO to establish the following standards for the exchange of digital files: TIFF/IT - P1 (ISO-12639) or PDF/X-1 (ANSI/CGATS.12-1).
Note: Digital files are now the preferred input for gravure printers. Supplied film separations must now be pre-approved by the publisher and gravure printers involved, and may result in additional processing charges to the supplier.
* For more detailed information on the exchange of digital files see "Generation and Exchange of Digital Files" in the SWOP Specifications section. More information and a perspective on the use of digital files is available in the General Reference Section on page 35.
There is one significant difference between GAA and SWOP specifications that users should be aware of. Gravure printing is capable of achieving the SWOP color gamut on both coated and some uncoated stocks. Therefore, the GAA Input Specifications for Publication Gravure apply to both coated and uncoated printing stocks. The degree to which the final gravure printed reproduction result matches the brightness, print smoothness and gloss of the color guide will be determined by the printing stock of the publication.
Gravure standard colors match SWOP colors, and are referred to as GAA/SWOP. The standard reference for these colors is the SWOP Hi-Lo Color References. Colorimetric data for these references is available through the GAA at no cost (GAA Colorimetric Specification for Publication Proofing and Printing-Revision 1.6 1992).
Screen angles and dot shapes should not be included in the supplied page file. With gravure printing, dot shapes and screen angles are controlled and limited by the engraving device and, therefore, cannot match the screening of a supplied file. It is the gravure printer's responsibility to resolve moiré pattern problems that occur during the engraving process or to notify the publisher if pattern problems of any kind cannot be resolved. The publisher, prepress supplier and ad agency are responsible for resolving solutions for input materials that cause or contribute to moire and other undesirable patterns that cannot be corrected by the printer.
Total Area Coverage (TAC)
The GAA endorses the 300% TAC requirement as specified by SWOP for web offset printing. However, 300% TAC is not a limiting factor for gravure printing and on uncoated stocks higher TAC may be preferred by some publishers.
Gray Component Replacement (GCR) and Undercolor Addition (UCA)
Due to the reduced opacity and increased porosity of uncoated stocks, GCR applications may not be suitable for all users of uncoated stocks. Therefore, the use of GCR on uncoated stocks is a matter to be resolved and pre-approved by all parties involved. For the minimum three-color UCA relationships, see the table on page 35.
As in offset preparation, the three-color balance (cyan, magenta, yellow) remaining under black or dark gray areas after GCR is applied must result in a visually neutral gray color.
Note: Although GCR can help in moderating unwanted color variation, it can, if used to excess, limit options for editorial color changes in prepress or interfere with color adjustments for precise match on press. It can also result in deep shadow and black areas that have insufficient gloss, lost detail or unwanted reversals. Experience has shown that GCR levels up to 60%, if done properly, can generally give problem free results. At GCR levels significantly above 60% it is recommended that both prepress supplier and print buyer use caution and perform testing as appropriate.
Critical Image Areas - Minimum Printable Dot
Colors composed of dot values at or below 5% are difficult to reproduce in any printing process. Halftone films suitable for offset publication printing will be suitable for gravure publication printing. To assure good tonal reproduction, picture edges and other image areas intended to be distinctly visible from the paper should be a minimum of 5% in the weakest component color.
Note: Although developments in digital plating and engraving technologies have improved tone reproduction control in the extreme highlights (less than 5% dot), designers should still be cautious in placing image components in this tonal range.
This precaution is necessary for two reasons:
1) All- digital production workflows are not yet universally employed in the graphic arts industry, and
2) Process Control cannot always guarantee precise tonal reproduction below 5%, depending on the printing process.
Type and Line Art
When supplying film, reverse type, surprint type and line art should be supplied as separate films. This will allow gravure printers some flexibility in providing the very best type reproduction possible. More complete information on the GAA Input Specifications for Publication Gravure is available from the Gravure Association of America, 1200-A Scottsville Road, Rochester, NY 14624. E-mail: firstname.lastname@example.org.
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